MANHATTAN — He's a truck driver and volunteer firefighter, but that didn't stop him from chasing after the man accused of driving a truck onto a Manhattan bike path and killing eight people.

William Harris was driving a truck down West Streeet Tuesday when he heard a collision and spotted Sayfullo Saipov step out into the intersection, two real-looking guns in hand. He got out of the truck and chased after Saipov.

"This is New York. You don't mess with us," Harris said. "I didn't think twice. I went after him and I had to stop him."

Video footage shows Harris chasing Saipov in the minutes before police arrived on scene.

"He kept screaming 'Allahu Akbar' and waving the guns around," Harris said. "I don't know if he was looking for another target or not, but he had to keep turning around and looking at me and running away from me."

Police arrived on scene and shot Saipov. Harris went down on his knees and put his hands on his head.

He told PIX11 he knew he had to do something when he saw what happened - his father told him to always protect the innocent.

"It feels good," he said. "Just stopping the bad guy."