She also said she was glad her son is now "in a place where he can no longer do harm to anyone."
"To the families of the victims, I am so, so very sorry that this has happened.
"My heart is broken."
She took no questions after the statement, which she gave to a reporter in New York.
“His actions have had a profound and everlasting effect on the families of the victims,” she said. “I don’t know why he did what he did, and I’ll never be able to ask him why."