U.S. Navy Yard shooter's mom apologizes for son's killing spree

Washington Navy Yard shooter Aaron Alexis's mother has apologized for her son's killing spree, and said she was glad that he could no longer harm anyone.

Cathleen Alexis read a statement at her Brooklyn home in which she said: "His actions have had a profound and everlasting effect on the families of the victims. I don't know why he did what he did, and I'll never be able to ask him why. Aaron is now in a place where he can no longer do harm to anyone, and for that I am glad."

Police has still not been able to judge the reason for the 34-year-old to go on a rampage killing 12 people at the Naval Sea Systems Command on Monday, New York Daily News reports.

According to the report, he carved his last words 'MY ELF WEAPON' into the shotgun he used to shoot up innocent people.

Alexis' stepfather Frank Calderon said his son was never the same after 9/11 when he saw the twin tower razed to the ground while coming up from the subway station.

Alexis had earlier claimed he was suffering from post-traumatic stress disorder (PTSD) from 9/11 when he was arrested in Seattle in 2004 for shooting out at a construction worker's tires.

A Rhode Island cop said Alexis claimed he heard voices through the wall of a hotel room and was followed by three suspicious people who were using a microwave machine to send vibrations into his body to keep him awake.

Alexis also showed up at a Veterans Affairs hospital in Providence complaining of insomnia, but he denied of any kinds of depressing thoughts that could harm himself or anyone.

Alexis was given security clearance and was allowed to continue working as a Navy contractor.

However, lawmakers were reluctant to act against the National Rifle Association (NRA) and their allies over stricter laws against personal weapons.