The Fort Hood shooting that took place Wednesday was the second since 2009, when U.S. Army psychiatrist and medical officer Nidal Malik Hasan killed 13 people and injured more than 30. Wednesday’s shooting of some 20 people played out very similarly, but with an important twist.

The suspect has tentatively been identified as Specialist Ivan Lopez, a soldier who had spent four months in Iraq in 2011 and was receiving treatment for depression and anxiety. Following his return from deployment, he was also undergoing evaluation for post-traumatic stress disorder (PTSD) — one of the most common psychiatric diagnoses given to war vets and, barring unknown personal or ideological motivations, a likely cause of Lopez’s spree.

Depression and anxiety are common in the U.S. — roughly 17 percent of American adults suffer from at least one depressive episode at some point in their lives — but one thing they don’t do is make people homicidal. People with major depressive disorder feel empty or sad. They lose interests in activities and being around people. They also have difficulty concentrating and making decisions. They may be irritable, but they aren’t impulsive.

That is, unless they suffer from another disorder, too. Lieutenant Mark Milley, the commanding officer at the base, told reporters Wednesday that Lopez had never received a formal diagnosis for PTSD, although Lopez himself had admitted to suffering a traumatic brain injury while in Iraq. Milley predicted that the actions of a man who probably had PTSD will likely be responsible for others experiencing it.

The shooting took place at roughly 4 p.m., when Lopez walked into a building on the base and opened fire. He got into a car, kept shooting, drove to another building, and began shooting again. He killed three people and injured 16 over the span of 15 to 20 minutes, officials said, before he confronted a military police officer and put the .45-caliber gun to his head and pulled the trigger. President Obama said he was “heartbroken” that another tragedy could occur on the base.

In reality, veteran-related suicides are a daily tragedy, even if they don’t happen in conjunction with a mass shooting. A recent analysis of a 2012 Veterans Admissions report, which found an average of 22 vets took their lives each day in 2009 and 2010, suggested that an estimated 1,829 vets had already committed suicide in 2014. The new figure, released by the Iraq and Afghanistan Veterans of America spurred the March 27 commemoration at the National Mall in Washington D.C., where vets convened to place one flag in the ground for each death suffered.

At nearly 2,000 dead already, the suicide rate among veterans, when adjusted for age and gender, is more than double that of the general population. Nearly one in every five suicides is a veteran, despite the group making up only 10 percent of the U.S. adult population.

Wednesday’s shooting was especially painful for residents on the base and in the surrounding area, who have just only recently begun to heal from the killings five years ago. Milley told reporters his initial reaction wasn’t disbelief, but rather to secure the site and keep everyone safe. Others, meanwhile, felt the pain of a healing wound ripped open.

“As a community, it’s like you’ve been kicked in the gut,” Killeen, Texas, Mayor Dan Corbin told reporters, according to CNN. “It can’t be happening again.”