A rookie Sacramento police officer was fatally shot during a domestic violence call and lay wounded for about 45 minutes as the gunman kept officers at bay with volleys of bullets, authorities said Thursday. Officer Tara O'Sullivan, 26, was shot Wednesday while helping a woman collect her belongings to leave her home.

As officers swarmed the area, the gunman continued firing and the standoff lasted about eight hours before he surrendered. Sacramento Police on Thursday identified the suspect as 45-year-old Adel Sambrano Ramos and said he's been booked on charges relating to O'Sullivan's murder.

"We are devastated," Deputy Chief Dave Peletta said at a news conference. "There are no words to convey the depth of sadness we feel or how heartbroken we are for the family of our young, brave officer."

Get Breaking News Delivered to Your Inbox

O'Sullivan and other officers arrived at the home at 5:41 p.m. Wednesday. A half-hour later the first shots were fired and O'Sullivan was hit. The woman she was helping was not hurt. The relationship between that woman and the gunman was not immediately known.

Sacramento Officer Tara O'Sullivan CBS Sacramento

It also was unclear if the gunman was on the scene when officers arrived or if he showed up while they were there. The suspect's brother, Orlando Ramos, told the Associated Press he has a history of domestic violence and drug abuse and has been in and out of jail for years.

The gunman continued firing a rifle-type weapon, police said. At 6:54 p.m., additional officers responded with an armored vehicle to rescue O'Sullivan.

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

Five minutes later, O'Sullivan was taken to UC Davis Medical Center, where she died.

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.

UPDATE- On Thursday, June 20, 2019, at 5:55 a.m., the Sacramento Police Department booked 45-year-old Adel Sambrano Ramos on charges relating to the murder of Sacramento Police Officer Tara O’Sullivan. Original Press Release: https://t.co/fMBuTo0TGM #sacpd pic.twitter.com/eG8ro1gFRP — Sacramento Police (@SacPolice) June 20, 2019

O'Sullivan graduated from the police academy in December and was working with a training officer. She was expected to be on her own in a couple of weeks, Peletta said.

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."

O'Sullivan grew up in the San Francisco Bay Area and graduated last year from Sacramento State University with a degree in child development.

In a Facebook post, Steinberg said O'Sullivan was in the first graduating class of a groundbreaking program at Sacramento State that "emphasizes the importance of inclusion and cultural competence for future law enforcement leaders — of which Tara undoubtedly would have been."

Before being hired as a Sacramento officer, O'Sullivan worked with the police department as part of a community service program providing crime prevention support.

Devastated members of the Sacramento State community held a press conference Thursday, describing O'Sullivan as a leader in the school's Law Enforcement Candidate Scholar's program. Sacramento State president Robert Nelsen cried as he called O'Sullivan a hero.

"She had a big heart, a strong mind, a great personality, she made you smile," Nelsen said. "She is exactly what we need in the police force."

He said the school community was planning on raising money for a scholarship in her honor.

"We will never forget her. She will always be a Hornet," Nelsen said. "And we will aspire to be as good as she is."