PASCO, Wash. » A homeless man who was shot and killed by officers at a busy intersection had thrown multiple rocks, hitting two officers, and had refused to put down other stones, authorities said Wednesday.

Officers used a stun gun on the man, but it had no effect, Pasco Police Chief Bob Metzger said at a news conference. Because of his "threatening" behavior, officers fired their guns, he said.

Metzger said he did not know whether a weapon was found.

The man killed was 35-year-old Antonio Zambrano-Montes, whose last address was a Pasco homeless shelter, said Franklin County Coroner Dan Blasdel.

Witnesses say the man was running away when he was shot. They told the Tri-City Herald the man had run about half a block when he was killed about 5 p.m. Tuesday near the Fiesta Foods store.

The shooting occurred after officers responded to a report of a man throwing rocks at cars at a busy intersection near a grocery store.

Dario Infante, 21, of Pasco, recorded video from a vehicle about 50 feet away as the scene unfolded. In an email interview, he said he decided to start recording when he saw an officer trying to use a stun gun on the man. Infante said he saw the man throw a few rocks at police officers but he didn’t see him hit any officers. Five "pops" are audible shortly after the video begins, and the man can be seen running away, across a street and down a sidewalk, pursued by three officers.

As the officers draw closer to the running man, he stops, turns around and faces them. Multiple "pops" are heard and the man falls to the ground.

"He didn’t throw any rocks after he started running," Infante said.

Several dozen people gathered at Pasco City Hall on Wednesday afternoon to raise concerns about the shooting.

The ACLU of Washington also issued a statement, calling the incident "very disturbing."

"Fleeing from police and not following an officer’s command should not be sufficient for a person to get shot," the group’s executive director, Kathleen Taylor. Deadly force should be used only as a last resort, she said.

Witness Ben Patrick told the newspaper police fired at the man as his back was turned.

"I really thought they were just going walk up and tackle or tase him," he said. "But they opened fire. His back was turned."

Patrick’s wife, Shannon, also said the man was running away. The shooting happened in front of her young children.

"He turned around to take off running and the cops just shot him," she said. "All he was trying to do was walk away."

Other witnesses heard officers give the man orders to stop and drop the rock. They said the man refused to listen.

Metzger has identified the three officers involved in the shooting. They were placed on leave for the investigation, a standard practice.

The Tri-City Special Investigation Unit, which will not include Pasco police, will investigate. Investigators are looking at cellphone video of the scene that has been posted online.

Carlos Sanchez, who witnessed the shooting from the grocery store parking lot, also said it looked like the man was running away from officers when he was killed.

"They started shooting and they kept on shooting him," he said.

Tuesday’s case was the fourth fatal shooting involving a Tri-City police officer in Pasco in the last six months. Officers have been cleared of any wrongdoing in all three of the previous cases.