Last October, staff at the Parkway Place group home in Blaine knew they had to keep a close watch on one of the four residents.

Drew Potosky's mother had called that evening, warning that her son -- who has a traumatic brain injury -- tried to jump out of his grandmother's car that day and might be suicidal. Less than a month earlier, Potosky had to be coaxed down after he tried to climb up on the railing of the home's second-floor deck in a possible suicide attempt, records show.

But on Oct. 5, Potosky was left alone on the same deck. A staff member heard a thump and ran to the railing. Potosky lay on the ground about 15 feet below, alive but suffering a broken shoulder and a new head injury that would put him in the hospital for a month. The case is under investigation by state regulators.

Potosky's mother, Valli Witte of Blaine, knew her 18-year-old son was having trouble adjusting to Parkway Place, but she was assured by staff that he would be monitored closely.

"They didn't follow through with anything they said they would do," Witte said.

Staff members did the best they could, according to the head of the nonprofit group that operates the home.

"Sometimes tragic things happen," said Tim Burkett, chief executive of People, Inc. "The staff immediately provided the level of supervision the mom had asked for. ... They didn't promise that Drew would be watched every second."

Burkett noted that his nonprofit served 6,500 mentally ill people last year in its adult foster care homes and other facilities. In 15 years, he said, People, Inc. has not lost a single client to suicide.

In October 2008, Potosky -- then 16 -- was struck by an SUV while riding his bike, his mother said. He was hospitalized for three months with broken bones and severe head injuries. It took him another three months to learn how to walk again.

Because of his brain injury, Potosky has tremors that make it difficult to do some daily tasks, and his temper can be volatile, according to his parents. After living at home for more than a year with the help of personal care attendants, Potosky and his parents agreed he was ready to move into a supervised setting outside the home.

With the help of a social worker, they chose Parkway Place, one of 4,806 adult foster care homes licensed in the state. Founded in 2009, the four-bed facility in Blaine serves adults with mental illness and other problems. Two employees are on duty 24 hours each day, helping residents with meals, medications and other needs.

State and county regulators have not cited the home for any license violations. Four complaints involving medication errors were resolved without corrective action, Anoka County records show.

Shortly after moving into the home, Potosky stopped calling his parents, his mother said. On Sept. 9, Witte got a call from the group home. After drinking coffee, Potosky become combative and climbed onto a patio chair on the outside deck, records show. A staff member was able to talk him down. In an internal report, employees characterized the incident as a possible expression of suicidal thoughts, records show.

After the incident, Witte said she told the Parkway Place staff that her son should never be left on the deck alone. If he was capable of caring for himself, Witte said, "I would have kept him in my house."

Burkett said Potosky showed "a new behavior symptom" when he attempted to climb on the railing in September. "In this case, our staff were able to provide an increased level of supervision and maintained his safety until his symptoms subsided," Burkett said. "My staff said it worked well."

Witte said she and her husband were still trying to find a new home for Potosky when he jumped off the deck again on Oct. 5. Earlier that day, Potosky went out to dinner with his grandmother. He became so agitated on his way back to the home that he got out of the car and started walking down Highway 65 at rush hour. He didn't get back in the car until the police showed up to investigate.

Witte quickly called Parkway Place to report what happened. Burkett acknowledged that employees were alerted, but he said Potosky wasn't exhibiting any unusual behavior at the time. Potosky was left alone on the deck a little before 8 p.m., when a staff member brought other residents back inside, he said.

Burkett said a few seconds elapsed before the staff member noticed Potosky was no longer on the porch.

Potosky told police that he "attempted suicide and he was really depressed," according to a staff report. Shortly after speaking to officers, he went into a seizure.

Potosky spent a month in the hospital. He now lives in a group home in Duluth that specializes in adults with traumatic brain injuries. His parents say the second head injury has worsened Potosky's tremors and set back his recovery.

On Oct. 8, Witte filed a complaint with the state Department of Human Services. The agency hoped to finish the investigation by Feb. 9, but a DHS investigator sent a letter to Potosky's parents saying "other investigations that involve higher risk of harm are being completed first."

The new target date: April 10.