SAN BERNARDINO, California — A brother-in-law of one of the San Bernardino shooters said the Christmas party massacre was "a personal act" unconnected to the culprit's Muslim faith and described him simply as "a bad person."
Farhan Khan said he had "no idea" what led to Wednesday's rampage, in which 14 people were killed. He added that Syed Rizwan Farook and his wife, Tashfeen Malik, were "a happy couple" who loved their baby daughter. The tot was left with her grandmother before the mass shooting.
In an interview with NBC News, Khan once more expressed sorrow to the victims' families and said he was "very upset and angry" at Farook for his actions.
"What's the outcome?" Khan asked. "You left your six-month-old daughter … in this life. Some people cannot have kids. God gave you a gift of a daughter. And you left that kid behind. What … what did you achieve?"
Khan, who is married to Farook's sister, also revealed that he had begun legal moves to adopt the orphaned girl.
He said Farook was not a political person and never gave any indication of what may have motivated him and his wife to attack the city's Inland Regional Center with four guns and explosives.
"I wish we could have … some slightest idea," Khan said.
Farook and Malik were killed in a shootout with police a few miles away more than four hours after the atrocity.
Authorities told NBC News Thursday that Farook appeared to have been radicalized and had been in touch with people in the Los Angeles area who have expressed jihadi-oriented views. Intelligence sources said he appeared to have been in communication with people overseas who are of interest to U.S. authorities.
However, Khan said Farook, 28, was "a good religious person … just like normal anybody would be," but insisted: "He was not radical."
He added: "It's his stupid action, nothing to do with religion at all. It's always going to be a question ... you know, why he did something like that. A normal person living with my family. Why would he do something like that?
"Did somebody brainwash him? Something snap him? What — did he have — a fight at work? And I'm waiting … to hear, like, you know, what really happened.
Khan continued: "Based on the stories it looked like that he went to the party then he then he left, and he was angry. Could be that. I mean, it could be he planned. God knows. I have no idea. And I really want to know what made him do something horrible like that."
Khan said the couple had lived in a "normal house" and led ordinary lives.
"Couches, TV, kitchen. I mean, you know, a play area, a treadmill to run ... He liked to work on cars. I mean, that was his hobby, to go buy a used car, work on it. He loved buying used Mustangs, fix it, and then sell it."
He said the family would have alerted authorities if they had the "slightest idea" something was wrong.
"I didn't see at all. Normal person … as normal as you can think. I mean, you know, a person that … go to work, come back home, you know, play with the kid, eat dinner, sleep. Normal person."
"My wife goes to work, my kid goes to school. And if something happened to them, some — someone there that day lost a husband, wife, kid, somebody," he said. "Especially in this time, you know, like Christmas, holiday time, which is, you know … everybody get together, spend time together.
Khan added: "My message is, you know, that I am with all those families. I understand … how they are going through right now, how sad they are. And my heart is with them. And … sorry that this has happened.
"It shouldn't happen. Something … stupid that something like this doesn't relate to my religion. I am Muslim. I'm a good person. And there's a lot of good Muslims there. He was a bad person, that was his personal act."
Alastair Jamieson contributed. This article originally appeared NBCNews.com.