The parolee who killed three Oakland police officers and left a fourth brain-dead over the weekend had been linked by DNA evidence to a rape the day before the shootings, authorities said.

Oakland police spokesman Jeff Thomason confirmed a report on the San Francisco Chronicle's Web site on Monday night that DNA from an
unsolved rape in Oakland earlier this year matched that of Lovelle Mixon.

Investigators got that information Friday, the day before Mixon opened fire on the officers following a routine traffic stop.

Police could not have immediately issued an arrest warrant for Mixon because investigators first needed to gather another sample of his DNA for comparison purposes, Lt. Kevin Wiley, who oversees the police sex crimes unit, told the Chronicle.

Police are investigating any connections to other rapes, Thomason said.

Earlier Monday, state Attorney General Jerry Brown said he will examine how 26-year-old Mixon was monitored following his release
from prison in November on a conviction for assault with a deadly weapon.

Mixon also was a suspect in a murder last year but was never charged, according to state prison officials.

"Mixon was certainly a character that needed more supervision," said Brown, the former mayor of Oakland. "In Oakland, the highway patrol has an office there, sheriff and police. And all those agencies should have a list of the more dangerous, threatening parolees so they can keep a watch on them."

Problems involving parolees from California's overcrowded prison system have long beset state officials who must monitor them, local officials who try to keep streets safe and federal authorities who enforce firearms and other laws.

Mixon was one of 164 Oakland parolees in mid-March who had outstanding arrest warrants for parole violations, state prison records show.

The city of 400,000 had more than 1,900 total parolees at the time, including nearly 300 who had been returned to custody or whose parole was about to be revoked.

Statewide, almost 17,000 of the nearly 125,000 parolees were wanted for violating their parole requirements, state records show.

Mixon's family members said he was upset that he was unable to find work, felt his parole officer was not helping him and feared he would be arrested for a parole violation.

Mixon was wanted for missing an appointment with his parole supervisor.

State prison officials said Mixon's parole officer was responsible for 70 parolees.

A caseload of that size is nearly unmanageable, and also not unusual, said Lance Corcoran, spokesman for California's prison guard union, which includes parole officers.

Too many parolees prevents officers from effectively monitoring or guiding them back into society, Corcoran said.

"There is no control," he said. "It's simply supervision, and supervision at distance."

Mixon was driving a 1995 Buick when motorcycle patrolmen Sgt. Mark Dunakin, 40, and Officer John Hege, 41, stopped him around 1 p.m. Saturday, police said. Dunakin was shot dead at the scene.

Hege was declared brain-dead over the weekend but remained on life
support Monday.

How someone could take down armed veteran officers with such lethal efficiency is a focus of the police department's investigation.

Experts said officers know traffic stops carry clear dangers.

"Motor(cycle) officers are at a tremendous risk. A police vehicle at least provides you with a modicum of cover," said Dave Smith, a retired Arizona police officer who leads seminars on police street survival.

Officers can take some steps to ensure their safety, Smith said.

During traffic stops, police often check vehicle records to find whether the driver has outstanding warrants.

But police have not disclosed how the shooting incident unfolded.

Police have not said why Mixon was pulled over, but relatives who talked to him on his cell phone just before the traffic stop said he was looking for a parking space.

After the first two officers were shot, Mixon fled to what his family said was a younger sister's apartment around the corner.

A SWAT team stormed the apartment around 3 p.m. Sgt. Ervin Romans,
43, and Sgt. Daniel Sakai, 35, were gunned down before officers
fatally shot Mixon.

The SWAT team had little choice but to try to take the suspect by force, experts said.

"They knew this was a killer who hadn't hesitated to kill uniformed police officers," said Joseph McNamara, retired San Jose police chief and a research fellow at Stanford University's Hoover Institution.

"The normal SWAT strategy of surrounding, containing, negotiating, trying to resolve the situation without violence has to change once the killing has begun," McNamara said. "Police strategy then changes to, they must go in."

How Mixon got the guns, including an assault weapon, used in the
shootings has not been disclosed.

California prison records show that authorities issued a warrant for Mixon's arrest after he failed to make a mandatory meeting with his parole officer on Feb. 19. Parole violators typically face five to nine months in prison, said Gordon Hinkle, a spokesman for the state Department of Corrections.

Meanwhile, downtown Oakland was quieter than usual Monday as shock from the shootings started to sink in.

At City Hall, where the flags flew at half-staff, a steady stream of mourners patiently lined up in the lobby to write their condolences in four books, one for each officer.

Oakland police Sgt. Mark Schmid used his lunch break to write down his thoughts. He said his colleagues are still struggling with the incident.

"This is the biggest tragedy ever to hit our department," Schmid said. "We're just numb and walking around like zombies. We feel each other's pain but we don't know how to explain it."