screenshot/NBC
Aaron Alexis, the 34-year-old Navy veteran who died in Monday's shootout, was being treated for his mental health issues, which also hearing voices in his head, family members told police.
Despite these issues, the Navy had not declared him mentally unfit, according to the AP.
While some friends reportedly expressed disbelief that Alexis could be the shooter, there's other evidence of mental instability in his past. In 2004, Alexis was arrested in Seattle fot
Alexis later told police he couldn't remember firing the weapon, and that he had a "blackout" fueled by anger. He was also arrested in Fort Worth in 2010 for discharging his weapon, according to that city's NBC affiliate.