The FBI has released footage of the Navy Yard gunman stalking the corridors in search of victims.
The shooter, Aaron Alexis, 34, believed he was being controlled by low frequency radio waves, an FBI spokeswoman said, BBC reports.
“At this point I can confirm that there are multiple indicators that Alexis held a delusional belief that he was being controlled or influenced by extremely low frequency, or ELF, electromagnetic waves,” spokeswoman Valerie Parlave said.
Alexis, who killed 12 people and was shot fatally by police, appeared calm when he entered the complex in Washington D.C.
On his gun, Alexis had written, “Better off this way!”
Authorities don’t believe Alexis was looking for anyone in particular.