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."

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.