A somber police motorcade carried a slain deputy's body away from the scene of a bloody rampage Wednesday as investigators tried to determine what set off a shooting and stabbing spree that left six people dead and four wounded.

The mother of suspect Isaac Zamora, who was released from jail less than a month ago, said he is "desperately mentally ill" and had been living in the woods. Dennise Zamora said one of those killed Tuesday was a sheriff's deputy who had tried to help their family for years.

Isaac Zamora, 28, was being held Wednesday on suspicion of first-degree murder and attempted first-degree murder and is being held on $5 million bail.

The shootings began close to Dennise Zamora's house near the small town of Alger, about 70 miles north of Seattle. They continued amid a high-speed police pursuit on Interstate 5 and ended in Mount Vernon, about 20 miles south of Alger, when Isaac Zamora surrendered at a sheriff's office.

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"Some of these are just random shootings," Trooper Keith Leary said.

A motorcade escorted a hearse bearing the body of Skagit County Deputy Sheriff Anne Jackson, 40, on Wednesday from Alger to a funeral home in Mount Vernon. Dozens of police cars and motorcycles joined in.

County court records show Zamora has a history of petty violence and theft, including one case in 2003 in which he was charged with biting the hand of an employee of a drug treatment center. That case was dismissed.

A host of questions remained unanswered Wednesday, including whether the suspect knew any of the victims, how the shootings apparently continued during the police chase and how Zamora managed to turn himself in rather than being arrested by one of the many officers pursuing him.

There are eight crime scenes being investigated by more than 100 people from 15 agencies, Leary said Wednesday.

"We're not speculating as to what happened," Leary said. "It's too early to tell what took place at each scene."

Dennise Zamora told The Associated Press by telephone that she felt for the families of the victims.

"I wish it would have been him or me that was killed," she said. "That's how deeply I feel about it."

She said she wanted people to know that "my son was desperately mentally ill and we've been trying to get him help."

She told The Seattle Times that her son had lived in the woods off and on for years, was unaware of his mental illness and resisted all efforts to get him to accept treatment. The nature of his illness was not immediately clear, but his mother told the newspaper her son had struggled with it since the family's house burned down more than a decade ago.

She said that Zamora was "agreeable" and "placid" Tuesday morning and that she didn't know what made him change. She also said she didn't know where he got the gun used in the shootings.

Jackson was shot while responding to a call from Dennise Zamora, who told the Times that she called after seeing her son going into and out of her neighbors' homes.

Also killed, in addition to Jackson, were an unidentified man shot at the same location near Alger; two male construction workers who were found shot nearby; and a 48-year-old woman found a few houses away, authorities said.

A motorist identified as Leroy Lange, 64, of Methow, was shot and killed along I-5 near a rest stop, said Everett police Sgt. Robert Goetz.

Dennise Zamora described Jackson as a sympathetic figure who had tried to help the family in the past.

"She was very gracious," she said. "She knew exactly what we were going through, said her brother was going through some similar stuff."

The first shootings were reported shortly after 2 p.m. Tuesday and the suspect was in custody at the Skagit County Sheriff's Office by about 4:30 p.m.

In the Alger area, a 56-year-old man was shot and wounded, and a 61-year-old man was stabbed, Goetz said. Neither injury was considered life-threatening.

From the Alger area, the armed man raced south on Interstate 5 at speeds in excess of 90 mph, with troopers, sheriff's deputies and Mount Vernon police in pursuit, Leary said. It was not immediately clear whether Zamora fired shots as he drove or if he pulled over.

At least two others were wounded, including a Washington state trooper shot while trying to stop the gunman on the freeway, the State Patrol said. A 37-year-old motorcyclist was shot in the arm at a Shell gas station.

The wounded trooper, identified as Troy Giddings, drove himself to a hospital and was released after treatment.

Zamora had just served a six-month jail sentence for drug possession in Skagit County. After he was released in early August, he was under the supervision of the state Corrections Department, whose officials said they haven't found any warning signs in his file.

"From what we've seen so far, we haven't been able to identify any red flags that he was on course to do anything like this," spokesman Chad Lewis said.

"He's had a long criminal history, but has only served time in juvenile facilities and county jails, not in state or federal prisons," Lewis said. "It's a long rap sheet, but nothing of this magnitude, nothing involving shootings."

Gov. Chris Gregoire called for an independent third-party review to be led by the head of the Washington Association of Sheriffs and Police Chiefs and a prosecutor to be appointed by the Washington Association of Prosecuting Attorneys.

Hours after the shootings, a group of residents gathered at the Alger Bar and Grill.

"It's devastating for this town," Steve Thomas said, "The people here are very law enforcement-friendly. It's very somber."