There is growing skepticism today about how much the family of Syed Farook knew about his attack in San Bernardino.
In an interview, Farook's father said his son had expressed support for ISIS.
"He said he shared the ideology of [ISIS leader Abu Bakr] al-Baghdadi to create an Islamic State, and he was fixated on Israel," the father, also named Syed Farook, told Italian newspaper La Stampa, USA Today reported.
But he added that his son was a "mama's boy."
He added: "I cannot forgive myself. Maybe if I had been at home, I would have found out and stopped him."
Farook's mother lived upstairs in the same house as her son and daughter-in-law, Tashfeen Malik, and their six-month-old daughter. She lived there as the couple built pipe bombs and gathering ammunition, which were later found in their garage.
The mother, Rafia Farook, was questioned by the FBI and said she knew nothing about the attack, which killed 14 people and wounded more than 20 others.
On Sunday, Attorney General Loretta Lynch said investigators are looking at the mother and son's relationship.
"Obviously, it's something that we're looking at very, very closely," she said on NBC's Meet the Press.
Donald Trump has also pointed the finger at the family, saying he didn't believe Farook's sister when she said she knew nothing of his plans.
"I thought she was lying so much," he said of a recent TV interview. "I’m good at this. I thought she was a total liar. She lied about him… She knew. A lot of other people knew too."
But the family has flatly denied knowing anything. Their lawyer spoke on their behalf at a press conference on Friday.
“They were totally shocked that this could take place,” said criminal defense attorney David Chesley. “None of the family knew of him as being extreme.”