The FBI revealed preliminary details of the Washington Navy Yard Shooting and that included the details that gunman, 34-year-old Aaron Alexis, used a customized Remington 870 shotgun as he searched for potential victims in Building 197 last week.

The FBI's Valerie Parlave confirmed that the barrel of the Remington shotgun was sawed-off and the words "End to the torment!" and "Not what yall say!" and "Better off this way!" and "My ELF weapon," were etched into the stock.

Remington Arms is Herkimer County's largest employer and America's oldest gunmaker.  FBI officials believe the etchings in the stock of the gun reinforce their beliefs that Alexis was delusional.

An FBI Press Release explains that the "ELF weapon" etching refers to electromagnetic waves:

"There are multiple indicators that Alexis held a delusional belief that he was being controlled or influenced by extremely low frequency (ELF) electromagnetic waves. The etching of 'My ELF weapon!' on the left side of the receiver of the Remington 870 shotgun is believed to reference these electromagnetic waves. In addition, a document retrieved from his electronic media stated, '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.'

"ELF technology was a legitimate program for naval sub-tonal submarine communications; however, conspiracy theories exist which misinterpret its application as the weaponization of remote neural frequencies for government monitoring and manipulation of unsuspecting citizens."

The FBI also released chilling video of Alexis which shows him entering the navy yard and looking for victims roaming through hallways and entering open doors.