Infographic by Jan Diehm for The Huffington Post. 
Additional research by Alissa Scheller and Katy Hall.

04/08/2014 |Huffington Post

Army Spc. Ivan Lopez, the veteran who fatally shot three people before taking his own life Wednesday at Fort Hood, Texas, is among a growing number of recent veterans who have committed violent crimes after returning from war.

Lopez, 34, was struggling with depression, anxiety and insomnia and was being evaluated for post-traumatic stress disorder, military officials said. Of the more than 2.6 million Americans who have served in Iraq and Afghanistan, it is estimated that about one in five have suffered from PTSD, according to data provided by the Department of Veterans Affairs.

Researchers and therapists have found that certain people who suffer from PTSD display anger and aggression, but there is no research that supports a link between war trauma and violence back home.

"[PTSD] can cause outbursts when someone is provoked, but it does not provoke mass murder," Dr. Charles R. Marmar, chairman of the department of psychiatry at New York University Langone Medical Center, told the Los Angeles Times.

The vast majority of veterans do not come home to commit violent crimes. The veteran population is no more violent than the general population, and veterans are many, many times more likely to harm themselves than they are to harm others. Still, each time a former service member takes the life of an American cit... -- often a loved one, as shown below -- people struggle to figure out how the tragedy could have been averted.

"Obviously we have a gap," U.S. Defense Secretary Chuck Hagel told reporters on Thursday. "Any time we lose an individual, something's gone wrong."

In 2008, The New York Times compiled a list of 121 cases in which veterans were charged with a killing after returning home, and Current TV, GOOD and MGMT.design collaborated to update the research in 2010. The Huffington Post collected data from these sources and more recent news articles to create the infographic below, which shows that at least 194 veterans have been charged with killings after returning from Iraq or Afghanistan. It also shows that there has been a concentration of such incidents around military bases. Our research may not be a complete tally, but these were the cases we could confirm.

CLARIFICATION: An earlier version of this story did not compare veteran violence to violence among the general population or veteran suicides. We regret the lack of contextual information in highlighting these tragedies.