WATCH: The FBI also released 30 seconds of chilling surveillance footage showing Alexis driving rental car into a Navy Yard parking garage, entering a glass front door of a building, and walking through several hallways with a shotgun.
Washington Navy Yard gunman Aaron Alexis acted alone and there is no indication he was trying to target specific individuals when he shot and killed 12 people during his bloody Sept. 16 rampage, the FBI said on Tuesday.
The FBI also released 30 seconds of chilling surveillance footage showing Alexis—who was later killed by law enforcement—driving his Toyota Prius rental car into a Navy Yard parking garage, entering through a glass front door, and walking through several hallways with a shotgun.
FBI Assistant Director in Charge Valerie Parlave told reporters that Alexis, working as a contractor for a private technology firm, had legitimate access to the Navy Yard through his work. He entered the building with a Remington 870 shotgun and obtained a Beretta handgun during the shooting.
The 34-year-old had etched a number of words on the shotgun, including “End the torment,” “”Not what yall say,” “Better off this way!” and “My ELF weapon.”
“There are indicators that Alexis was prepared to die during the attack and that he accepted death as the inevitable consequence of his actions,” said Parlave.
Ronald C. Machen Jr., a U.S. Attorney for the District of Columbia, said there were indications Alexis was “mentally unstable.”
Parlave said Alexis likely held a “delusional belief” that he was being controlled by extremely low frequency (ELF) electromagnetic waves. The carving “ELF” in his shotgun is believed to reference that. In addition, an electronic document was found by authorities in which Alexis claimed “Ultra low frequency attack is what I’ve been subject to for the last 3 months, and to be perfectly honest that is what has driven me to this.”
Parlave explained that ELF technology was a legitimate program used for naval sub-tonal submarine communications. There are some conspiracy theories, she said, which “misinterpret its application as the weaponization of remote neural frequencies for government monitoring and manipulation of unsuspecting citizens.”
The FBI also gave more details about Alexis’ last few days. He arrived in the Washington D.C. area on Aug 25 and stayed at a hotel in Bethesda, Maryland until Aug 31. From Aug 31 to Sept. 7, he stayed at a hotel in Arlington Virginia, then moved to the Residence Inn in Southwest D.C. until the day of the shooting. He began work at the Navy Yard on Sept. 9.
The Remington 870 shotgun and ammunition was purchased at a gun store in Northern Virginia.
The FBI said investigators were still investigating Alexis’ motivations for the shooting.