A Washington state homeless man had thrown rocks and hit two officers before he was shot and killed by police at a busy intersection, authorities said Wednesday.

Pasco, Wash. Police Chief Bob Metzger said authorities had used a stun gun on the man, but it was ineffective. Officers fired their guns because of his "threatening" behavior, he said.

Witnesses say, 35-year-old Antonio Zambrano-Montes was running away when he was shot by police. The Tri-City Herald reports the man ran about a half of a block before he was killed Tuesday outside a grocery store.

Zambrano-Montes' last known address was at a homeless shelter.

In an e-mail interview with The Associated Press, Dario Infante, 21, said he recorded video of the scene. Infante said he saw the homeless man throw rocks at the officers, but they did not strike them. The man can be seen running away being 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.

The American Civil Liberties Union of Washington issued a statement Wednesday 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.

Three officers involved in the shooting were placed on leave for the investigation, Metzger said.

Tuesday's shooting was the fourth officer-involved killing in Pasco in the last six months. All officers have been cleared of any wrong doing in the previous cases.

The Associated Press contributed to this report