NEW YORK — The mother of the man who killed 12 people at the Washington Navy Yard says she is “so, so very sorry that this has happened.”

Cathleen Alexis said Wednesday in New York City that she does not know why her son, Aaron, did what he did and she will never be able to ask him.

The mother read a statement at her home in Brooklyn. She concluded, “My heart is broken.”

Thirty-four-year-old Aaron Alexis opened fire at the Navy Yard on Monday before he was killed in a shootout with police.

Authorities say he had been suffering a host of serious mental problems including paranoia and a sleep disorder.