PLANO, Texas (CBSDFW.COM) – The stepmother of the gunman shot and killed by security officers Monday outside the Earle Cabell Federal Courthouse in downtown Dallas said she had no idea Brian Clyde wanted to commit mass murder.

“It was so out of the blue,” said Heather Clyde. “Not near the surface of who Brian was to us.”

She said he was “lovable and quirky.”

Heather Clyde – Brian Clyde’s stepmother (Steve Pickett – CBS 11)

Heather Clyde, and Brian’s father, Paul Clyde, consoled each other outside their Plano home Wednesday afternoon.

Heather said they didn’t even recognize the photos of the partially-masked man who tried to shoot his way into the federal building, which houses several government agencies and 300 employees.

Federal security officers shot and killed him before he could get inside.

“We are so grateful no one was hurt or killed,” Heather said. That would have been a whole realm of Hell added.”

The FBI has yet to figure out the motive for Clyde’s armed attack and his stepmother told CBS 11, she saw nothing, not in his social media posts or his interactions with them, that suggested he would try to commit mass murder.

Brian Clyde

“We just wanted everyone to know we are flabbergasted as everyone else is,” Heather said. “He just wasn’t the person who is there downtown Monday morning, just not who we knew.”

Heather Clyde said she and her husband think Brian might have been trying to commit suicide, but they hadn’t seen any signs of depression or anger.

“That’s our feeling. He knew there had been a shooting down there, a well armed area.  That’s the only thing we can derive from his actions,” said Heather.

Brian Clyde had recently graduated from Del Mar College in Corpus Christi with an Associate in Applied Science degree in Nondestructive Testing Technology.