NYC Ax Attacker Was Consumed by Desire to Strike U.S. Authority Figures, Police Say

— -- In the days since the brazen Oct. 23 daylight ax attack on NYPD cops, investigators have pieced together the final days and weeks in the life in attacker Zale Thompson, 32, who was shot and killed by police defending themselves.

Two sources briefed on the case tell ABC News that Thompson's history paints the picture of a man consumed by jihadi philosophy and a desire to attack U.S. government and authority figures, egged on by the brazen attack on Canada's parliament a day before.

“As of last Thursday, detectives had found 277 sites he visited within last nine months that had something to do with al Qaeda, ISIS, beheadings or jihad,” said one police source. “He’s been all over the charts.”

Thompson, in just seven seconds, hit two uniform cops as they were taking photos with passersby alongside a second pair of officers on patrol. Cops have dismissed early suspicion that the people who asked for the pictures had set up the officers. Instead, police sources said it appears -- based on a review of previously unreleased street-surveillance video and witness accounts -- that Thompson had been stalking the cops for a time, waiting patiently until the moment to strike arrived.

“There’s video, very distant, about two blocks up, that shows him at the top of the frame,” one of the sources said. “He stays there about two minutes. Then, he bends over and then bolts, charges down the street, charging at the cops with the ax. You can see him watching, down the block.”

Witnesses told police that when Thompson bent down he reached into a backpack and pulled out the ax.

“The two pairs of cops were patrolling separately but they came together,” said one source. “Very evidently, he was waiting, he was watching him. And then when he saw them together, in the alcove in front of the buildings taking the picture, he figured ‘now’s the time.’”

In addition to the websites viewed by the attacker, sources said his computer showed a rambling “manifesto” in which Thompson wrote “seek them out, watch them and then attack them. Chop off the head of the beast. If we can’t do it ‘there,’ we have to do it here.”

About five days before the attack, Thompson locked himself in a room in his father’s home, where he did little but view jihadi websites until his father threw him out on Oct. 21, police sources said.

“The guy was angry at authority, angry at the establishment,” one source said. “And so he’s in there basically getting hypnotized by the computer. Talk about brainwashing. This guy sat in his room for days at least three days straight, closed the door and just sat in front of his computer.”

NYPD spokesman Steve Davis told ABC News he cannot discuss specifics of the investigation, except to say that detectives are confident that Thompson was acting alone without specific direction from a terror leader elsewhere. That, however, just proves how dangerous such “lone wolves” are, Davis noted.

“The investigation is continuing,” Davis said. “The further we get into this we are confident that, if he were directly inspired or directly recruited by a known quantity, that would have come out by know. It's pretty clear he was radicalized by himself. But in a way that's more bothersome than the people that are recruited by the real deal because you can’t see these people.”