Los Angeles police investigators are trying to piece together how a highly determined attacker eluded officers watching a Mid-City apartment and managed to kill a woman who had just filed a domestic violence complaint.

Wilshire Division officers who specialize in domestic abuse were on the lookout for the man after taking Flor Medrano's report, counseling her and returning her to her Cochran Avenue apartment Wednesday evening.

The officers escorted Medrano, 30, to her door, checked to make sure the apartment appeared safe and then returned to their unmarked patrol car to watch for the suspect, officials said.

The officers later tried to check on Medrano via cellphone and tell her they were leaving but were cut off. When they reestablished contact and heard screaming, the officers rushed to the apartment and saw a man stabbing Medrano.

Unable to gain entry through a metal security door, the officers fired through a front window, fatally wounding the attacker, according to police sources who asked not to be named because of the ongoing investigation.

Both Medrano, whose 3-year-old daughter was away with relatives during the attack, and the man, who was not immediately identified, were pronounced dead at Cedars- Sinai Medical Center.

The man apparently scaled the roof of the apartment building and somehow entered the unit through a small rear bathroom window, Capt. Eric Davis said.

"This is no small feat," Davis added. "This man was destined to cause harm to Ms. Medrano. . . . In this instance, domestic violence has reared its ugly head in the worst form."

Davis defended his officers, saying they "were diligent in their efforts. They determined this was a predator and he needed to be removed from the streets. . . . The officers were exerting extra effort relative to a follow-up investigation. They were very dedicated and they went above as far as initiative."

The officers built a relationship with the victim over several hours and are "touched by this tragedy," he said.

The chain of events began Wednesday afternoon when Medrano flagged down patrol officers, saying she had been raped, according to the Police Department sources.

At the Wilshire station, she declined to go forward with the charges, the sources said. But she told officers that she had been seeing the man off and on and that he was abusing her physically.

During the course of the investigation, the suspect sent Medrano several text messages, leading investigators to believe he was possibly in the area. Officers went to Medrano's apartment but did not find him, Davis said.

Medrano was counseled about seeking a restraining order and going to a domestic violence shelter, but said she wanted to go home, sources said.

At 10:45 p.m., officers agreed to take Medrano to her apartment. They still hoped to catch the man.

They escorted her to her door, the "location was secure" and Medrano had the only key, Davis said. The sources said officers searched the apartment's interior.

The officers didn't sense anything was wrong until 11:25 p.m., when they phoned Medrano and were cut off.

Maria Olivia Rivera, a neighbor, told The Times she heard screams and then saw the police officers bounding upstairs to Medrano's apartment. "Open the door! Open the door!" Rivera recalled the officers yelling.

"They were trying so bad to get in because I think they were watching through the window what was going on," she said. Rivera entered her own apartment and then heard a shot.

After the shooting, Davis said, the officers were able to get inside and try to aid Medrano and her assailant.

Neighbors described the victim as a friendly woman who moved into the mixed neighborhood of Spanish-style homes and apartments with her daughter a few months ago.

Medrano was "always smiling, always happy," Rivera said.

But Wednesday, Medrano seemed rushed and scared, she added.

Medrano had been planning her daughter's fourth birthday party, said Jasmin Gomez, 20, whose daughters played with the girl.

The department is conducting two investigations, one of Medrano's killing and the other of the officer-involved shooting, officials said.

LAPD procedures require police to take reports from domestic violence victims and offer a range of options to ensure their protection, including staying in a shelter for battered women.

Victims are also counseled on legal options, such as seeking restraining orders against abusers. Medrano declined to pursue those options, sources said, and even though officers were not obligated to take her home, they did.

The officers also checked the apartment and waited outside, none of which is required, officials said.

Elizabeth Vera, director of Community Support Services in L.A., who has spent 15 years working domestic violence issues, said it is common for victims of domestic violence to turn down police assistance.