This month’s shooting deaths of police in Baton Rouge, La., and Dallas by former servicemembers who saw combat in Iraq and Afghanistan comes as the Army is trying to better understand why up to 40 percent of troops return from war struggling with anger and aggression.

Police say rage may have driven Gavin Long, 29, who served five years in the Marine Corps, to kill three police Sunday and Micah Xavier Johnson, 25, a former Army reservist, to fatally shoot five officers on July 7.

Whether there is a link between their military service and the shootings is unknown. And military researchers have been studying the issue of anger for almost a decade.

Since 2007, a series of studies have shown 14 percent to 40 percent of troops surveyed after returning from war or while in the war zone report signs of anger such as kicking, smashing or throwing things, or threatening someone with physical violence. Anywhere from 4% to 18% were getting into fights.

Long, who was deployed to Iraq for eight months in 2008 and rose to the rank of sergeant, had previously posted a video on the Internet, describing protests against police as futile. He said he wanted to follow in the footsteps of Nat Turner, who led a slave revolt in 1831, and Malcolm X, a black Muslim civil rights leader during the 1950s and early ’60s.

Micah Xavier Johnson, an African-American former Army reservist who served seven months in Afghanistan, told a negotiator during an hours-long standoff with law enforcement in Dallas he was angry over recent police shootings of black people and wanted to kill white officers. When negotiations failed, police used a robot carrying an explosive device to kill Johnson.

Read More- Military Times

Image courtesy of AP