The apparent murder-suicide at Lackland Air Force Base in Texas turns attention once again to fatal shootings at US military installations in recent years, most notably the Fort Hood shooting of 2009 that ended in 13 dead and 32 wounded.
Since September 2008, Fort Hood Army Base in Texas has been the sight of four fatal shooting incidents by US service members – including Major Nidal Malik Hasan's mass shooting in November 2009 – as well as one foiled bomb plot.
READ MORE: Two people killed at Lackland AFB in Texas, murder-suicide suspected
Fort Hood, September 2008
Iraq war veteran Specialist Jody Michael Wirawan, 22, shot himself after killing his superior, Lieutenant Robert Bartlett Fletcher, 24. Fletcher and another Fort Hood officer had gone to Wirawan's apartment to discuss milling military equipment, according to police in Killeen, Texas, when an altercation led to the shooting.
Wirawan, who was facing a second tour of duty in Iraq, according to the Alaska Dispatch News, was attempting to leave the US Army at the time.
Fort Hood, November 2009
Using an automatic pistol, Major Nidal Malik Hasan opened fire in a medical deployment center of Fort Hood, killing 13 and wounding 32 others in what is considered the largest mass murder event at a US military installation.
Hasan, who was due to be deployed to Afghanistan in a few weeks, was shot in the process by a police officer. He later admitted to the shooting, telling a US military court that “Evidence will show I was on the wrong side of America’s war and I later switched sides."
He was found guilty of murder in 2013 and was sentenced to death. He is currently incarcerated at the United States Disciplinary Barracks in Fort Leavenworth, Kansas.
Hasan was a US Army psychiatrist and Medical Corps Major who was born in Arlington, Virginia. An FBI investigation found that Hasan had email communication with Anwar al-Awlaki, an influential American cleric who was an alleged recruiter for Al-Qaeda and was eventually killed in 2011 by a US drone strike in Yemen. Following the shooting, Awlaki had called Hasan a "hero" and "man of conscience."
Fort Bragg, June 2012
Iraq and Afghanistan veteran Specialist Ricky Elder shot himself a day after fatally shooting Lieutenant Colonel Roy L. Tisdale and wounding one other at a safety briefing at Fort Bragg in North Carolina. Just prior to the shootings, Elder had been charged with larceny and was awaiting a court martial, according to CBS News. He was also set to be sentenced for aggravated battery in Reno County, Kansas, after allegedly punching a woman in 2010.
Elder, who enlisted in the Army in 2004, was deployed to Iraq from October 2006 to November 2007 and to Afghanistan from September 2010 to July 2011.
Navy Yard in Washington, DC, September 2013
Aaron Alexis, a former government contractor, fatally shot 12 people and injured three others before a DC police officer killed him at the headquarters of the Naval Sea Systems Command at Washington Navy Yard. Armed with a 12-gauge shotgun and a 9mm semi-automatic pistol, Alexis stalked through Building #197 just days after an alleged workplace dispute, the FBI reported, though no one "he worked for or worked with" was targeted. The 12 victims killed in the shooting were all at least 46 years old.
The FBI reported that Alexis was under "the delusional belief that he was being controlled or influenced by extremely low frequency electromagnetic waves," though Alexis was cleared of any mental health issues just weeks before the shooting spree.
Alexis, 34, joined the US Navy in May 2007 and served until his honorable discharge in January 2011. During his stint in the Navy, he was cited for misconduct at least eight times, including a incident in which he illegally discharged a weapon in Fort Worth in 2010, shooting a hole through his ceiling and into a neighbor's apartment.
Fort Hood, April 2014
Iraq war veteran Specialist Ivan Lopez, 34, shot himself after killing three and injuring more than a dozen others with a .45 semi-automatic handgun. Lopez reportedly opened fire after he was denied a ten-day leave to address "family matters," which led to a a verbal altercation with other soldiers.
READ MORE: Fort Hood shooter was on anti-depression medication
Lopez had been treated for numerous mental health issues, including depression and anxiety, prior to being transferred to Fort Hood in February 2014. He was also being evaluated – but had yet to be diagnosed – for post-traumatic stress disorder in connection with his four-month deployment in Iraq in 2011.
“Obviously this reopens the pain of what happened at Fort Hood five years ago,” President Barack Obama said in April 2014, referencing the 2009 shooting.
Marine Corps Reserve Center in Tennessee, July 2015
Muhammad Youssef Abdulazeez, 24, a naturalized citizen from Kuwait, killed four marines and injured three others during a rampage that took place at two separate military installations – a military recruitment center and a Navy and Marines reserve center – in Chattanooga, Tennessee.
Abdulazeez died during a shootout with police. An FBI investigation of the shooting concluded that "there is no doubt that [Abdulazeez] was inspired, motivated by foreign terrorist organization propaganda," FBI director James Comey said in December 2015.
The four marines who perished belonged to an artillery reserve unit that served three tours in the Iraq War. During its first deployment in 2004-2005, the unit took part in the Battle of Fallujah, firing more rounds than any artillery battery since Vietnam.
Abdulazeez was employed at Superior Essex wire and cable company and had lived near Chattanooga for at least 17 years prior to the incident. His family said that the person who committed “this horrible crime was not the son we knew and loved,” and that he had suffered from depression and substance abuse problems.
According to the New York Times, Abdullazeez's father was investigated for ties to a terrorist organization at some point in his past. He had been included on a terrorist watch list and questioned by authorities, but was ultimately removed from the list.