The Sacramento gunman arrested for allegedly killing a female police officer has been identified as a 45-year-old father-of-two and a grandfather with a long history of violence against women.

Police say officer Tara O'Sullivan, 26, was helping a woman gather her belongings to move out of a home in the North Sacramento neighborhood when she was shot on Wednesday evening.

Sgt. Vance Chandler said an armored vehicle was brought in to rescue the wounded officer, but it took more than 45 minutes to get her to a hospital because the gunman kept firing a rifle.

The standoff in the 500 block of Redwood Avenue ended early Thursday morning when the suspect surrendered to police.

The Sacramento Police Department officially identified the suspect late Thursday afternoon as 45-year-old Adel Sambrano Ramos.

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Police in Sacramento named Adel Sambrano Ramos, 45 (left), as the man who shot and killed rookie officer Tara O'Sullivan, 26 (right) while she was helping a victim of domestic violence

Online jail records show Ramos was booked into the county's mail jail facility at 5.55am on counts of felony murder and misdemeanor battery.

The 5-foot-9, 185-pound Ramos is being held without bail pending his next court appearance scheduled for June 24.

According to reporting from the Sacramento Bee, Ramos has a criminal record dating back to at least 1995, which includes multiple charges of domestic violence and battery, theft and DUI.

His most recent run-in with the law preceding Wednesday's incident took place last September, when he was arrested for allegedly attacking a young woman at the same home on Redwood Avenue where the police standoff took place overnight.

Tara O'Sullivan is pictured during her graduation ceremony at College Park High School in Concord, California, in 2011

Tara O'Sullivan decorated her mortar board with her police academy plans at College Park High School's commencement ceremony in Concord, California. O'Sullivan, 26, was shot Wednesday June 19, 2019, while helping a woman collect her belongings to leave her home

In that case, Ramos was charged with 'willfully and unlawfully [using] force and violence.' Given that the charge was a misdemeanor, Ramos was released pending a trial and barred from having contact with the victim.

A warrant for his arrest in that case was issued on June 10.

Records indicate that Ramos was accused by his wife of domestic violence in 2003.

In April 2007, Ramos again was accused of the same crime targeting another woman.

On Thursday, the man's estranged wife, Sarah Ramos, told the Sacramento Bee that he was a good man and a good father to their two children. The couple, who had been married for a decade before separating, also have a granddaughter.

Ramos' neighbor told the paper that the 45-year-old murder suspect has always been polite, and enjoyed hunting and fishing.

The gunman surrendered to police at around 2am on Thursday, after an eight-hour standoff

O'Sullivan had been partnered with a training officer when she was shot just before 6 p.m. He did not offer any more information.

O'Sullivan had only been a police officer for six months when she was killed, after graduating from the force's police academy in December.

Chandler said nobody else was hurt and the woman who was being helped by the officer escaped unharmed.

'Our officers maintained cover in safe positions until we were able to get an armored vehicle in the area,' said Sgt. Vance Chandler.

KTXL-TV reported that the officer was hit and then pinned down in a yard.

The network added that officers tried to reach her, but a man with a rifle was shooting from another home.

The gunfire kept O'Sullivan's colleagues away for 45 minutes.

Stephen Nasta, a professor at the John Jay College of Criminal Justice and a former inspector with the New York Police Department, said taking 45 minutes to reach a wounded officer was 'unacceptable.'

If officers couldn't immediately get an armored police vehicle to the scene, he said, they should have commandeered a bank armored vehicle, bus or heavy construction equipment.

'If there's somebody shot, lying on the ground, you have to do everything you can,' Nasta said.

If no such vehicle was available, he said he would expect officers to use a diversionary tactic such as firing at the home, deploying smoke grenades or breaking a door or window in another part of the home to distract the gunman as other officers rescued the downed officer.

Just before 7pm, officer O'Sullivan was brought to UC Davis Medical Center, where she later succumbed to her injuries following surgery.

The suspect continued firing at officers through the night. Sometime after 11pm, a police negotiator was able to make contact with the gunman after delivering a cell phone to him by a robot, reported Sacramento Bee.

A sheriff's officer in tactical gear is pictured on the scene of the standoff in Sacramento

The gunman surrendered to police early Thursday morning after a tense eight-hour standoff

A law enforcement officer climbs into a tactical vehicle during the standoff Wednesday

Sacramento police officers respond to the shooting on Redwood Avenue in the Noralto neighborhood Wednesday

At around 1am, the gunman barricaded inside the house signaled that he would be willing to surrender.

Just before 2am, the man stepped out of the back door of the house holding a cell phone and a shirt in his hands, and was taken into police custody. So far, he has not been identified.

At a press conference held prior to the suspect's surrender, Deputy Chief Dave Peletta confirmed O'Sullivan's death.

She had been partnered with a training officer when she was shot just before 6pm. He did not offer any more information.

O'Sullivan had been working for the city since January 2018.

A law enforcement officer mans a barricade near a home on Redwood Avenue during the standoff overnight

A Sacramento police officer puts up crime scene tape near the home where the gunman had taken refuge

A man and woman watch as law enforcement officers surround a home where a gunman has taken refuge

Police earlier called in a SWAT team and surrounded the home, warning residents to stay away or keep indoors because of the active shooter

She was part of the first class of graduates of Sacramento State's Law Enforcement Candidate Scholars program in 2017 and went on to the Sacramento Police Academy.

Mayor Darrell Steinberg issued a statement to O'Sullivan's parents, family and fellow officers.

'As a father I am grieving with you,' he said. 'As mayor of the city she swore to protect, our city is heartbroken and we are here for you every step of the way.'

California Governor Gavin Newsom also offered his condolences and ordered flags at the State Capitol to be flown at half-staff in O'Sullivan's honor.

In a statement, Sacramento Police Department said: 'It is with a broken heart that we have to share with all of you that earlier today we lost one of our own.

'While on a call for service in North Sacramento, Officer Tara O’Sullivan was shot and killed. She gave her young life while protecting our community.

'We are devastated tonight. There are no words to convey the depth of the sadness we feel, or how heartbroken we are for the family of our young, brave officer.

O'Sullivan (center) was part of the first class of graduates of Sacramento State's Law Enforcement Candidate Scholars program in 2017

O'Sullivan (four from left) had been serving the City of Sacramento since January 2018

'The men and women of our police department will continue to do our jobs to protect our community, and we will draw strength from the courage of Tara.

'Our hearts are with Tara’s family, whose pain can hardly be imagined. Please hold her family in your thoughts and prayers.'

O'Sullivan is the first Sacramento police officer to have died in the line of duty in 20 years.