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The FBI says it has helped to disrupt or prevent nearly 150 shootings and violent attacks this year, in part by steering potential gunmen toward mental health professionals. It's an achievement that stands out during a year when President Barack Obama made curbing gun violence a priority, yet has had little success in getting new restrictions enacted.

There have been hundreds of these disruptions since 2011, Attorney General Eric Holder recently told an audience of police chiefs, touting the behind-the-scenes work of a small FBI unit based out of Quantico, Va. In most cases, the FBI has helped potential offenders get access to mental health care.

Preventing mass shootings through threat assessments and treatment is an unusual tactic for an agency known for its crime fighting and not for interventions. One year after the deadly mass shooting at a Connecticut elementary school, the White House's biggest efforts to curb gun violence — attempts to reinstate the assault weapons ban and expand background checks for all gun purchases — failed without congressional support.

Mass shootings like the rampages in Newtown, Conn., the Washington, D.C., Navy Yard and the Aurora, Colo., movie theater do not represent the majority of gun violence. Yet when they do occur, the impact is high. And many times there's the question of whether the shooter had adequate mental health treatment to prevent it from happening. Yet, in the national discourse about reducing gun violence, mental health treatment has received much less attention than banning assault weapons.

The FBI's Behavioral Analysis Unit, for years, has been working with state and local authorities to profile potential offenders with the goal of preventing violent crimes like mass shootings. The "prevented" shootings and violent attacks from January through November of this year represent 148 cases that a division of that unit, the Behavioral Threat Assessment Center, has conferred on during 2013. And that number is up 33 percent from 2012, Andre Simmons, unit chief of the center, said in an interview with The Associated Press.

In the past year, this unit has received about three new cases a week referred by federal, state, local and campus law enforcement, schools, businesses and houses of worship, Simmons said.

The Behavioral Threat Assessment Center gets involved when someone notifies law enforcement, for example, about some troubling behavior, and law enforcement reaches out to the center to help assess the situation.

"The people around that subject often become fearful that that outcome is catastrophic act of violence, such as an active shooting or some type of mass attack," Simmons said.

The center is staffed by agents and analysts of the FBI, the U.S. Capitol Police, the Bureau of Alcohol, Firearms, Tobacco and Explosives and a psychiatrist. It helps the local officials assess the threat the person of concern poses. And then the center recommends how to proceed. Depending how far along the person is on the "pathway to violence," Simmons said, the center makes recommendations based on the specific case. The recommendations could be arrest, if the person is involved in illegal activity, but most often, it's getting that person access to mental health care, he said.

As an example, Simmons referred to a case his unit consulted on a few years back. There was a man at a university who began to display bizarre behaviors coupled with an increasing interest in firearms, Simmons said. This man created a makeshift shooting range in the basement of his home where he lived with roommates, and he used pictures of the roommates as bull's-eyes for target practice. He also was involved in animal abuse, Simmons said, and he was making statements that were troubling. Collecting firearms and target practice are not illegal activities, but the roommates feared for their safety. So they alerted university authorities, Simmons said.

The university reached out to the FBI behavioral analysts and worked with them to develop a strategy. Working with mental health officials and campus police, a "caretaking" interview was arranged with the man, Simmons said. And that meeting resulted in a voluntary admission to a psychiatric facility.

"Once in that facility, he was deemed to be of such compromised state, that it turned into an involuntary evaluation," Simmons said. "And the attending physician noted as well that it was not really a question of if he would attack, but when, given the statements that he made and the thoughts he was disclosing."

The FBI would not provide specific details of this case or others they've consulted on because many are ongoing and involve people who have not been charged with crimes.

The Behavioral Threat Assessment Center operates with the knowledge that mass shootings like Newtown are uncommon, and that's important, said Ronald Schouten, a psychiatrist at Massachusetts General Hospital and expert on threat assessments.

"These occur very rarely, and there's no profile," Schouten said of those who carry out the shootings.

The center was launched in the fall of 2010. The unit's existence is not yet common knowledge around the country. But awareness is growing, as the FBI has recently been sponsoring two-day conferences about the threat of active shooters, Simmons said.

Having a mental illness does not mean that a person is predisposed to violent behavior, Simmons said. So a person's history and surroundings are an important part of assessing the threat.

"And we recognize that for many individuals, the coping strategies may be overwhelmed and they may lose the ability to see an alternative to violence," he said.

One year ago, a 20-year-old gunman, Adam Lanza, shot his way into Sandy Hook Elementary School and massacred 20 children and six women with a semi-automatic rifle. He also killed his mother in their Newtown home before driving to the school. He committed suicide as police arrived at the scene, and authorities still do not know his motive. Since the shooting, Lanza has been described as "troubled." Investigators said his fascination with violence was apparent to teachers and other acquaintances.

After that tragedy, President Barack Obama spoke to the nation about reducing gun violence.

"We're going to need to work on making access to mental health care at least as easy as access to a gun," he said five days after the deadly shooting.

The Behavioral Threat Assessment Center has not been promoted by the White House as one of its major efforts to reduce gun violence. Instead, it's continued the behind-the-scenes work it's been doing for the past three years. And referrals keep coming in.