A man went on a two-hour shooting rampage in the US today, killing six people and wounding two others before turning himself in.

The violence began when a Skagit County Sheriff's deputy was shot and killed while responding to a disturbance in the small town of Alger in the northwest of Washington State on Tuesday afternoon, according to police trooper Keith Leary. Another person was killed at the same location.

Two construction workers were then shot and killed during the shooting spree, and a third body was found nearby. A motorist driving on a motorway was then allegedly shot by the suspect as he fled, leading police in a chase at speeds in excess of 90mph (145kmp).

Two other people, including a state trooper who was reportedly grazed in the arm by a bullet, and a motorcyclist who was shot at a petrol station, were wounded in the shooting, and are being treated in hospital.

The suspect later turned himself into police, less than three hours after the first shooting was reported.

Police are "99 percent sure" the man is Isaac Zamora, 28, who has a lengthy criminal record and was released from Skagit County jail on August 6, said police spokesman Chad Lewis.

Mr Zamora's mother told the Associated Press that said she had tried repeatedly to get help for her son, whom she described as "desperately mentally ill."

"We're so devastated for the families," Dennise Zamora she told the news agency. "I wish it would have been him or me that was killed. That's how deeply I feel about it."

Officer Leary said a motive for the shootings remained unclear.

"It's going to be some time before we know what happened," he said.

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