BEDFORD-STUYVESANT - The mother of the Washington Navy Yard gunman has broken her silence for the first time since her son killed 12 people Monday.

Cathleen Alexis spoke from her Bed-Stuy home on Putnam Avenue, saying that she doesn't know why her son, 34-year-old Aaron Alexis, did what he did and that she is "so, so very sorry."

She said answers to her son's murderous rampage are in short supply and her only relief is the knowledge that the killing is over.

Law enforcement sources revealed that the former Navy reservist was being treating for mental illness prior to the fatal rampage that also wounded eight people. They say he was receiving treatment from the Department of Veterans Affairs for paranoia, a sleep disorder and for hearing harassing voices.

Reports say Alexis sought help for insomnia from a hospital for veterans, but denied struggling with anxiety. He also denied having thoughts of harming himself or others.

Information on Alexis' mental problems has reignited a volatile national debate on gun control. President Barack Obama reiterated on Tuesday the need for tougher background checks for guns, but advocates in the Senate say they're several votes shy of passing any legislation that would better prevent felons or the mentally ill from buying weapons.