Robert King had threatened to kill his wife before, and he’d hit her before, but nothing quite like this.

The burly man knocked his wife to the ground, grabbed her neck, and squeezed. He shrugged off a nephew trying to stop him.

“I heard something pop in my head,” he said, “and I got up and looked at my hands, and looked at my wife. She was gagging and gasping for air. And I called the cops …

“I thought I killed my wife.”

The psyche of men who kill their spouses or girlfriends is a growing concern in Minnesota, where a spike in domestic homicides has provoked a jump in calls to domestic abuse shelters.

Details of the cases of Mandy ­Matula, Danielle Jelinek and Kira Steger — three Twin Cities women presumably killed by their boyfriends or spouse — show how difficult it is to predict what type of abuser is capable of lethal ­violence. But experts said there are some telltale warnings signs that should be heeded in order to reduce the death toll.

Nine boyfriends or husbands have allegedly killed their partners so far this year. The count is 10 if it includes Matula, 24, whose body remains missing and whose boyfriend shot himself before police could interview him. The state is on pace to double the 2012 total of 14 deaths.

“The level of violence I’m seeing? Things are getting worse, not better,” said Heidi Carlson, who leads the men’s counseling program for the Domestic Abuse Project in Minneapolis.

The profile of a typical abuser is a man who has been victimized himself in childhood and has developed such insecurity that he has an overwhelming desire to control everything around him — especially the routines and whereabouts of his spouse or girlfriend.

The abuser who is more likely to kill owns a gun, and brandishes it during arguments. He is likely to have made death threats to his partner in the past, and to have raped or choked her.

A less common but telling risk is when an abuser hurts a pregnant partner, said Neil Websdale, a Northern Arizona University professor considered one of the nation’s top experts on domestic homicide. “Pregnancy is a tender time between couples. A man that is willing to assault and abuse his pregnant partner, I think, is ­logically more dangerous.”

Predicting a killer

Even with this information, preventing domestic homicide is challenging because the majority of men — even those known to be abusive — don’t kill their partners. And there is no research to date indicating that an abuser who has made 10 death threats is riskier than a man who has made one threat.

Recent Minnesota cases have involved men with warning signs such as gun ownership, but no history of aggression, said Aaron Milgrom, director of therapy for the Domestic Abuse Project.

“These appear to be emerging as the guys who are most lethal,” he said. “The police were never called on them. They never went to treatment. The neighbors thought they were OK or just kept to themselves. And then they burst forth into the news. … It’s really problematic for us.”

The deaths of Matula, Jelinek and Steger reflect this complexity. Matula’s suspected killer was not known by others to be abusive; he was well-known to the Matula family and beloved by some of her relatives. Jelinek’s family, by contrast, described at least three incidents in which Aaron Schnagl hurt Danielle, including one incident when he choked her. Schnagl is in prison on a probation violation and is a person of interest in Jelinek’s death.

While the abuser capable of murder is harder to identify, the timing of fatal abuse is easier to predict. An estimated seven in 10 fatal abuse cases occur after women have left abusive ­partners or threatened to leave.

Matula and Steger, whose legal last name remained Steger after her marriage, both reportedly were trying to separate from their partners.

The threat of losing a spouse represents the ultimate loss of control to abusers, so they “up the ante” in the intensity of their abuse, Carlson said. The risk of domestic homicide is greatest in the first three months of a breakup, and especially in the first week.

“In my mind, I can’t live without this person,” Carlson said. “So I take the next step. … These men are desperate. They’re on the edge.”

Almost attempted murder

King, now 37, said his abusive tendencies came from his teen years when he was in gangs that habitually mistreated women. Abuse emerged in many forms in the relationship with his wife — from his insistence on knowing her whereabouts, to his comments that undermined her in front of their kids, to physical confrontations when she defied him.

But he never thought he was capable of lethal violence until the night five years ago when his wife came home and tried to wake him by slapping him.

King knows how fortunate he is that his wife is alive and he isn’t in prison. He recalled watching as a judge thumbed through a stack of medical records regarding his wife’s injury. Inspecting X-rays and MRI results, the judge said the severity of injuries would determine whether King would be charged with attempted murder.

“He looks down, looks up, looks down, looks up, and he goes, ‘Somebody is looking down on you,’ ” King recalled, “ ‘because there’s no fractures, no tears, no bruising.’ ”

Men underestimate the level of violence they commit.

At a men’s nonviolence class in Duluth, Scott Miller draws a line on a board with “staring” at one end and “homicide” at the other. At first, most men claim they are at the far end of the scale and are low risks. By the end, they admit they are more violent than recognized, said Miller, who runs the Duluth Model’s domestic abuse intervention project. Kicking in a door might not seem like a lethal action until the men envision what might happen if their partners are on the other side.

Many victims in their 20s

Even with this year’s spike in domestic homicides, it isn’t clear that the state is seeing a growing problem. Annual femicide reports, assembled since 1989 by the Minnesota Coalition for Battered Women, have shown the number of women dying from domestic violence vary from a yearly low of 12 to a high of 40.

The number of women needing hospital care for domestic abuse injuries also hasn’t changed, according to the state Department of Health. Around 950 women have needed such treatment each year for the past decade. The hospital data, assembled at the Star Tribune’s request, show a higher rate of victims in their early 20s.

It’s unclear whether young abusers are at greater risk of killing or inflicting severe injuries than others. Carlson worries that childhood exposure to violent media content puts them at risk, but the state femicide reports show a wide range in the ages of men who kill.

Websdale, the national expert, said there is some data showing that young women are at greater risk of domestic homicide — especially if their abusive partners are 10 or more years older than they are. Matula, Jelinek and Steger were 30 or younger. Steger’s husband, who has been charged with second-degree murder, is 39.

Calls to domestic abuse shelters spiked with the publicity of the searches for the women. Most came from people worried about relatives and how they can safely remove themselves from abusive relationships.

King, who lives in Cloquet, learned of the deaths from a news report about Matula playing softball at the University of Minnesota Duluth. He believes the solution is greater public education that reaches abusive men and corrects their ­attitudes toward women.

Counseling has helped him shed the controlling attitudes that fueled his anger and abuse. After a separation, he reconciled with his wife and they are raising their three children together. Now at counseling, he sees new young men coming in with the dangerous attitudes he once had.

“As a man, you feel like you need to be in control of certain situations,” he said. “Sometimes, you just have to back off. It’s not all about you anymore.”