"These are thousands of human tragedies that could be avoided with even minimal oversight," said Nancy Fitzsimons, a professor at Minnesota State University, Mankato, and chair of a state committee on abuse and neglect of vulnerable adults. "It's distressing enough to move a loved one into a facility. People should not have to worry about them being attacked by a roommate."

Left unchecked, a single abusive resident can cause immense pain and distress.

At an assisted-living facility in Hugo, an elderly male resident with dementia tormented a female resident for six months in 2015 before the staff intervened, according to a state investigative report. The man stole her walker, hit her so hard that her eyeglasses flew off, stabbed her in the eyebrow with a pen and smashed a glass picture frame over her head, sending glass all over the floor, the report said.

The facility's only response was to increase the assailant's dose of antipsychotic medication, state records show.

Altercations between residents have grown more frequent and more serious in recent years as senior care facilities have allowed more seniors with psychiatric problems to live alongside frail elderly residents — often in assisted-living facilities that are lightly regulated by the state.

In addition, nursing homes are admitting a much higher percentage of patients for short-term rehabilitation stays. These patients tend to be younger, stronger and more volatile than longer-term patients, elder care researchers have found.

Across the country, complaints to state regulators about physical and sexual assaults between residents have increased 50 percent since 2012, exceeding any other category of abuse complaints in elder care facilities, federal data shows. Yet the problem of resident-on-resident abuse is rarely addressed, and state and federal regulators have taken few steps to prevent it.

"It sounds awful to say this, but it's probably going to take a senator's mother or father to be involved in an incident like this for policymakers to wake up and take notice," said Nicholas Castle, a University of Pittsburgh professor who has studied the issue. "Not a lot of folks realize that the biggest threat to your loved one's safety … could be sleeping in the room next door."

Faced with the growing problem, state officials and leaders of the senior care industry say they are in the early stages of developing a coordinated response. Care Providers of Minnesota, a trade association, recently floated the idea of creating a statewide network of mental health counselors who could respond to escalating tensions in nursing homes and state-licensed assisted-living facilities. The counselors would step in during times of crisis and train facility staff to de-escalate tense situations and detect triggers to aggressive behavior.

Officials at the Health Department have also begun looking for patterns that might explain the surge in altercations between residents.

"We need to be way more proactive on this issue, because the current approach is clearly not working," said Patti Cullen, president and chief executive of Care Providers.

Paulette Bakeberg had just drifted off to sleep in her room at the GoldenLiving Center in Delano on a summer evening last year when a fellow resident with dementia burst into her room and insisted that she was sleeping in the wrong bed, according to police and state records.

Bakeberg told the man to leave. He grabbed her by the wrist and pulled her to the floor.

Just weeks earlier, Bakeberg, 70, had undergone surgery to relieve swelling inside her skull after a stroke. On the night of the attack, her brain was still partly exposed, covered only by a flap of skin held together with 45 staples. When her attacker yanked her by the arm, Bakeberg's injured skull hit the floor, according to a police report. As blood poured down her face and nightgown, Bakeberg recalls, she managed to reach out and pull an emergency cord dangling near her bed.

For several weeks after the assault, Bakeberg was too traumatized to sleep alone; her husband and daughter Shelly took shifts sleeping on a sofa in her bedroom until she could be moved to a different facility.

"All I can remember is the soft spot on my head hitting the floor, and then an aide calling out, 'There's blood all over!' " she said.

Since the attack, Bakeberg has suffered such intense headaches that she has learned to ease the strain by shutting her eyes, even while playing with her 16 grandchildren. She learned to crochet with one hand because paralysis had seized the left side of her body. And she learned to endure a recurring nightmare in which she screams for help as her attacker approaches, but no words pass her lips.

"I keep praying that my life will go back to the way it was before the attack," she said.

Health Department inspectors took nearly a year to investigate the assault, and in the end decided it wasn't serious enough to warrant a fine or any other penalty.

In its final investigative report, the agency noted that the assailant "was aggressive toward staff" and had a history of wandering. Even so, inspectors determined that the man's behavior was "unexpected," and the facility was not at fault because he had never acted aggressively toward another resident.

Investigators also concluded that Bakeberg, a former financial adviser, suffered a "minor scalp contusion" and that the incident did not constitute maltreatment because it did not affect her lifestyle. The assailant was eventually transferred to a different senior home and was never charged with a crime, records show.

The state's findings shocked Bakeberg and her husband of 50 years, Dennis. Bakeberg said she is in near constant pain and still suffers mental trauma. Once strong, her voice has become a faint whisper. And while she is trying to move on, Bakeberg said she continues to replay the incident in her mind.

"I should be walking right now," she said with obvious frustration, while maneuvering her wheelchair during a visit to the family's home overlooking Lake Osakis in west central Minnesota. "It's like I'm a child, learning how to ride a bike all over again."

Prosecuting resident-on-resident abuse can be difficult. The victims often suffer from dementia, and the perpetrators themselves may be elderly or unwell. But Minnesota law authorizes the Health Department to take steps against the care facility — by issuing corrective orders or even suspending or revoking its license — if inspectors believe the home has failed to protect residents.

Yet even in cases of severe abuse, the Health Department seldom holds anyone accountable for resident-on-resident violence.

A review of state investigations by the Star Tribune shows that when victims and their families file formal complaints alleging a failure by the facility — such as poor supervision or understaffing — state investigators typically conclude that the violence could not have been foreseen, and exonerate the facility.

Researchers who study resident-on-resident abuse say there are warning signs, and they usually present themselves long before violence erupts.

"The idea that assaults like this are completely unexpected is simply not credible," said Eilon Caspi, a gerontologist and dementia behavior specialist from Minneapolis who has spent two decades studying resident-to-resident incidents. "Most of these incidents are truly preventable."

This summer, Caspi completed a first-of-its-kind study of deaths from resident-on-resident violence in nursing homes, analyzing 100 fatalities worldwide since 1988. He found a series of patterns. In a majority of the deaths, the assailant had previously been involved in at least one aggressive incident toward another person. Nearly half involved roommates. And 61 percent of the attacks were never witnessed by facility staff, suggesting a lack of supervision, he said. In all of the cases, at least one of the residents had dementia.

"You can only keep a lid on a boiling pot so long," Caspi said. "If you don't respond to the mild altercations, the tension builds and builds until it reaches a breaking point."

One reason for the rising number of altercations is the rapid growth of assisted-living facilities, which operate under much less regulation than nursing homes, elder care researchers say.

Over the past 20 years, many assisted-living facilities have come to resemble skilled nursing homes, taking on more patients with dementia and other severe conditions. But unlike nursing homes, assisted-living facilities are not subject to minimum federal staffing levels or annual inspections by regulators.

Enticed by the lax regulation, assisted-living facilities have grown rapidly: Today, Minnesota has nearly 60,000 assisted-living residents, compared with 28,000 people in nursing homes.

All too often, these facilities give insufficient thought to the suitability of roommates and react too late when they do not get along, said Castle of the University of Pittsburgh.

"You have thousands of people being put in close quarters with strangers, often against their will, and the level of frustration can be off the charts," he said. "Facilities are quick to assess residents for the risk of falling, but then ignore their potential for violence."

Rachel Reeves, a spokeswoman for the National Center for Assisted Living, an industry group, said such conflicts are a subset of the broader national challenge to find suitable care for patients with mental illness. But she acknowledged the importance of assessing residents before mingling frail elderly patients and those with volatile personalities.

"Assisted living communities are committed to ensuring the safety and well-being of residents," Reeves said in a statement. "As with any setting, bringing together individuals with different personalities and care needs may occasionally cause conflict, and any altercations should be dealt with swiftly and surely."

James Parker bears the scars, literally, of a roommate who proved to be unsuitable.

Parker was admitted to a Golden Valley nursing home in late 2015 while recovering from a stroke. Soon he and his daughter, Monia, begged administrators for a different roommate.

Parker, who is 77, had been placed in a room with a 46-year-old man who had a history of psychiatric problems and violent outbursts, including a conviction for assault, according to police and court records. He threw objects across the room, slammed doors and regularly taunted Parker, family members said, and at other times paced the halls yelling when staff failed to satisfy his demands.

Unable to stop the behavior, Parker told two staff members that he was contemplating suicide.

"I told them that if I have to spend one more night with that man, then I would kill myself," Parker said. "And they still ignored me."

A social worker at the nursing home assured Parker that managers would draw up a plan to address his concerns, according to records in a civil case. But the plan never materialized, Parker's daughter said.

Tensions erupted one December morning while Parker was eating breakfast on the edge of his bed. His roommate slammed the door, according to a state investigation, and Parker responded by telling him to "be a man, not a child."

When Parker refused to take back the comment, the roommate charged at him, repeatedly punching him in the head and face, causing a deep laceration to his head, according to a police report. Parker was rushed to North Memorial Medical Center in Robbinsdale, where he underwent emergency surgery to stop bleeding in his brain.

When Golden Valley police arrived at the nursing home, they found the assailant sitting in the cafeteria, calmly talking with other residents as if nothing had happened. The officers who took him into custody noted that he still had blood on his hands, according to police records.

Before the attack, Parker was on a path to recovery from his stroke. Now, he is bedridden in a different nursing home. He cannot walk or eat without assistance, and relatives said they expect he will never be able to live independently. An 8-inch scar runs down the back of his head where he received 19 stitches.

"He nearly beat the life out of me," said Parker, breaking down in tears. "It happened so fast that I couldn't even raise my hands to protect myself."

The family filed a complaint with the Health Department, alleging neglect and poor supervision on the part of the facility. But after investigating the incident for nearly a year, state investigators concluded that "staff could not have anticipated the unexpected and sudden altercation," and said the facility was not responsible for the violence.

"How many times were we supposed to warn them?" his daughter, Monia, asked.

Officials with Milwaukee-based Fortis Management Group, which operates the Golden Valley nursing home, did not respond to phone and e-mail requests over three weeks for comment on the case.

Parker's assailant was charged with assault, but his case was put on hold because he has been ruled mentally incompetent to stand trial. Today, nearly two years after the incident, there is no court disposition of the case.

On a recent afternoon, Parker struggled to stay alert in his nursing home bed as his daughter and granddaughter fussed over him, feeding him fresh-cooked fried chicken and iced tea as they clipped his toenails. "I'm good enough and up to snuff!" Parker kept repeating with a wide grin.

Then he drifted off to sleep, his jagged scar visible in the sunlight streaming through the window.

Chris.Serres@startribune.com 612-673-4308David.Joles@startribune.com 612-673-7904