After nearly 14 years on active military duty, Sgt. 1st Class Paula Walker, 33, shot herself in the head on Fort Lee’s military base. She’d been stationed there since December 2011.

Prior to the incident, Walker was reportedly irate, throwing objects around in a room she barricaded herself in. Fort Lee was on an hour-long lockdown while negotiators tried to talk her down. Walker was rushed to the VCU Medical Center where she was pronounced dead.

The gun in question was not a military-issued weapon, which, it turns out, is not unlikely for Fort Lee. If a gun is properly registered, it is allowed on base. Otherwise, there are currently no metal detectors, according to a report from CBS 6 News.

In 2009, Walker was stationed at Fort Eustis (also in Virginia) when former Major Nidal Hasan, a military psychiatrist, killed 13 people and injured more than 30 on Ford Hood. U.S World News and Report referenced an archived interview Walker gave regarding the incident, in which she said, “People are people. They go through things in life. They either handle stresses in a good way or in a bad way.”

The reason for Walker’s suicide is currently being investigated, but this comment might suggest she was suffering from post-traumatic stress disorder (PTSD). According to the National Alliance on Mental Illness, unprocessed feelings associated with the terror and memories of trauma can appear unexpectedly and unpredictably later on. One of the three general symptoms is increased arousal, where someone can experience difficulty falling asleep, concentering, increased vigilance and outburst or anger and irritability.

Though Walker was serving as a human resources specialist on Fort Lee, she served in Iraq from 2007 to 2008. So if it does come out she was suffering from PTSD — 20 percent of Iraqi veterans do — it will be a sobering reminder that fighting on the frontlines is not the only trigger.

The truth is PTSD can be triggered both externally (the situations a person encounters) and internally (memories and emotions). Anger, anxiety, frustration, feeling out of control, and a racing heart beat are all examples of internal triggers. It’s not just an active soldier’s problem.

Knowing this, and raising awareness, is what will help prevent the estimated 22 military suicides that occur each day.