People used to leave their doors unlocked and take the kids for strolls along the city's quiet streets north of downtown. Not anymore. A mysterious serial killer who has claimed five female victims - and who police say will likely strike again - has driven people inside, behind locked doors and windows.

There, some people have taken to bathing with revolvers nearby, aware that some of the victims were in the shower or had just gotten out when they were stabbed to death with their own kitchen knives.Outside, the city's normally peaceful University City and Clairemont neighborhoods are filled with fear.

"I can't go out in the street or open the door," said Lupe Reyes, a 23-year-old live-in baby sitter in University City. "Before, we could take the children out to play and we could take walks. But now we can't go out because of the fear that he's out there.

Reyes, like so many other women in the neighborhood, is wary - frightened of the man who since January has boldly entered the homes of five women between the hours of 8 a.m. and 1 p.m.

In each instance, the killer entered through an unlocked door or window, say police who are conducting the largest manhunt in San Diego history.

About 30 investigators are sifting through more than 2,000 leads that came in after the most recent murders, the Sept. 13 slayings of Pamela Gail Clark, 42, and her 18-year-old daughter, Amber.

Amber Clark and three other victims were brunettes, aged 18 to 21. Authorities speculate that Pamela Clark was killed because she happened to be home with her daughter.

The first victim was 20-year-old Tiffany Paige Schultz, a San Diego State University student who moonlighted as a nude dancer. She was slain in her Clairemont apartment in January.

Janene Marie Weinhold, 21, who lived just two blocks away, was killed two months later. Holly Suzanne Tarr, an 18-year-old high school student from Okemos, Mich., was in town to visit her brother when she was killed in April.

Experts have put together a profile of the killer that describes him as a disorganized opportunist who probably picks his victims on the spot. They say the fact he uses the victims' own knives as weapons indicates the murders aren't well planned.

"We don't have the lead that we need," said police Capt. Dick Toneck. "We're still waiting for someone to come forward and say, `I know this person.' "

In the meantime, Toneck said, police believe the killer will strike again.

"I don't think this person is going to leave town," Toneck said. "I believe he's going to do what he's doing. We're fully aware of the time constraints. We're fully aware that this could take place anywhere."