Motorcycle officer John Hege, 41, was declared brain dead Sunday morning at Highland Hospital in Oakland and remained on life support to preserve his organs for donation.

His death made Saturday's shootings in East Oakland the deadliest attacks on California law enforcement in almost four decades.

According to authorities, Lovelle Mixon used a semiautomatic pistol to shoot and kill Hege and Sgt. Mark Dunakin, 40, two motorcycle officers who pulled him over during a routine traffic stop. Two hours later, Mixon, who was holed up in his sister's nearby apartment, opened fire with an AK-47 assault rifle, killing SWAT team sergeants Ervin Romans, 43, and Daniel Sakai, 35.

Another SWAT team officer, Sgt. Pat Gonzales, also was shot: A bullet ripped through his left shoulder, and another ricocheted off his helmet. He was treated for his injuries and released.

The chaotic shootout occurred in a darkened apartment filled with smoke from officers' nonlethal shock grenades and dust from bullets ripping through drywall. It ended when SWAT team officers returned fired and killed Mixon, authorities said.

On Sunday, Gov. Arnold Schwarzenegger flew in from Washington, D.C., to offer condolences and to meet with Oakland Mayor Ron Dellums and Howard Jordan, Oakland's acting police chief. Investigators tried to figure out why Mixon would commit such a crime.

Law enforcement authorities revealed Sunday that Mixon had been investigated last year in another homicide case in Alameda County. Details of that slaying were not immediately released, but prosecutors found there was not enough evidence to charge him.

Outburst puzzles police

Oakland investigators said they were not aware of Mixon's possible connection to the earlier slaying. They said they were perplexed about what triggered Mixon's sudden outburst of violence against their officers.

"This is a strange one," said Oakland police Capt. Steve Tull, who is overseeing the investigation. "We don't know what his motivation is." If authorities found he had violated the conditions of his parole, Mixon would have faced at most six months in prison, Tull said.

Mixon "weighed six months" against his own life and the lives of the officers, Tull said.

Relatives of Mixon gathered Sunday morning at an East Oakland home where the parolee had been living until recently. They publicly apologized to the officers' families and said they were shocked by the sudden burst of violence that has devastated their city.

"He's not a monster," said his sister, 24-year-old Enjoli Mixon, who said her 4-year-old daughter's bedroom in a small apartment on 74th Avenue was the scene of much of the bloodshed. It was there, police said, where Mixon fired through a closet wall at a team of SWAT officers, who then shot and killed him. "I don't want people to think he's a monster. He's just not. He's just not."

"We're crushed that this happened," added the gunman's grandmother, Mary Mixon. "Our hearts and prayers go out to the officers' families. ... This shouldn't have happened."

Assault conviction in 2002

Lovelle Mixon was convicted in 2002 of assault with a deadly weapon after an armed robbery in San Francisco, family members said. He served time in San Francisco County Jail and Corcoran State Prison. He had been released on parole in 2007, then was sent back to prison for nine months in 2008 after he had violated his parole. His attorney in the assault case, Lisa DewBerry, declined comment Sunday.

His family said that while he was behind bars, Mixon married his childhood girlfriend, Amara Langston, and worked briefly as a janitor in Hayward once he got out. He was most recently released from prison in November, his family said.

Then, about three weeks ago, Mixon skipped a home visit from his parole officer, his family said. Mixon's grandmother said he had gotten angry at his parole officer because the agent had missed earlier appointments. Gordon Hinkle, a spokesman for the state Department of Corrections and Rehabilitation, said the family's assertion that the parole agent had missed a meeting was "highly unlikely," but added that he is researching the matter. He said the department had issued a no-bail, parole revocation warrant for Mixon's arrest after he failed to appear for a meeting with his parole officer.

"We did pick him up previously, (and) he has been looked at as a suspect in other serious crimes," Hinkle said. "He was a suspect in a murder, but due to lack of evidence, on a homicide, he was charged with other violations."

Mary Mixon recalled that her grandson said at one point that he was even willing to go back to prison as a way to get a new parole officer. She said, she did not know where her grandson had been staying for the past few weeks.

According to police, Saturday's violence began about 1:08 p.m. when two motorcycle officers, Dunakin and Hege, were shot after stopping a burgundy 1995 Buick in the 7400 block of MacArthur Boulevard in East Oakland, not far from the Eastmont Town Center.

Officer's radio contact

Dunakin had radioed in that he was going to make the stop, notifying authorities of the vehicle involved. He walked up to Mixon, asking for his driver's license. Dunakin then brought the paperwork back to his motorcycle. It was at this point that Mixon sprung out and fired a semiautomatic pistol, hitting both officers, authorities said.

Mixon's relatives said that when he was stopped by the police motorcycles, Mixon was apparently looking for a parking space. He had bought the car a week earlier from someone in San Francisco.

Mixon was having a phone conversation with his uncle, Curtis Mixon, just before the first shooting. "He said, 'The police just pulled up behind me. Let's see what's going on. I'll hit you back.' "

Curtis Mixon said, "He never hit me back."

About two hours after the first shooting, about 200 officers from the Oakland police, Alameda County Sheriff's Office, BART police and California Highway Patrol combed the area for the suspect. Acting on an informant's tip, a SWAT team raided the apartment of Mixon's sister.

Romans was shot almost immediately, as was Gonzales, who continued to battle a gunman the officers couldn't see.

At one point, an Alameda County sheriff's deputy outside the apartment went in with a rifle and joined the fray after he saw officers carrying out a wounded comrade, said Harry Stern, an attorney representing officers in the case.

Stern said that during the gunfight, the deputy and three other officers closed in on Mixon in a back bedroom, which was pitch black, smoky and dusty. Mixon was shooting from a closet, police said.

One officer was fatally shot in the bedroom before Mixon was killed.

"It was a remarkable display of heroism and galantry in the face of unfathomable destruction," said Stern, who did not name the officers.

Enjoli Mixon said she was not at her apartment when her brother holed up there. But another sister, 16-year-old Reynete Mixon, was at the apartment.

Reynete said she was in the bathroom when police officers bashed in the front door, causing her to drop to the floor. The officers ran toward her, she said, shouting and throwing grenades that shredded her pajama bottoms and caused her legs to bleed.

Soon, she said, she ran out of the apartment. As officers moved her across the street, she said she heard gunfire.

"I thought off the top that he was dead," Reynete said of her brother.

Chronicle staff writer Henry K. Lee contributed to this report. E-mail the writers at dbulwa@sfchronicle.com and jvanderbeken@sfchronicle.com.

This article appeared on page A - 1 of the San Francisco Chronicle