A serial rapist has attacked nearly a dozen women in the city, targeting those who live alone and tracking their movements before breaking into apartments in the middle of the night.

The 11 attacks since November are creating fear in the city and prompting the Phoenix Police Department (search) to create a 50-member task force and tip hotline dedicated solely to finding the rapist.

Patrol officers have spent the past several days fanning out across the city to pass out composite sketches and warn residents that even the simplest precautions could make a difference.

"If you're a woman who lives by herself, you have to make certain — you can't just think you did — you have to check that everything is locked," said Detective Tony Morales. "It's the biggest thing you can do to protect yourself."

Authorities are calling the suspect the "A.M. Rapist" (search) since he strikes overnight and quietly gains entry through unlocked doors and windows.

"When the women wake up, he's already standing in their bedroom," Morales said.

Police said they have linked the man to 10 sexual assaults through "biological evidence" and have linked him to one attempted assault.

Seven of the rapes occurred in north Phoenix within miles from each other — two occurred at one complex. Another three took place in east Phoenix, with the suspect attacking two women on separate nights in one complex.

Morales said the suspect appears to methodically select his victims. All were white women ranging in age from 20 to 46 and almost all lived alone.

"It's pretty obvious he's watching or stalking them," Morales said. "He knows personal information about them and has made comments that he doesn't just pick women on the spot."

In the most recent attack on July 22, the woman was raped as her two young children slept in the next room, Morales said.

Dr. Steven Pitt, a forensic psychiatrist at the University of Arizona, said that as serial offenders (search) become more proficient at their crime, they become more brazen.

"It's intoxicating for a serial offender to have repeated success," Pitt said. "Their mode of operation evolves."

Police said all those attacked lived in large condo and apartment complexes, making it easier to prowl unnoticed. Sprawling master-planned apartment "communities" — many contain hundreds of units and take up several city blocks — are common around the metro area.

Judith Weston, 65, who lives at a north Phoenix apartment complex targeted at least twice by the rapist, said police knocked on her door Thursday night and left a sketch. She said her complex also has taken additional safety steps by passing out window locks to all residents.

"I'd like to think I'm pretty safe," said Weston, who lives alone. "But people forget and get careless."

Pitt said a serial offender's proficiency, and subsequent overconfidence, usually leads to his becoming sloppy. That's when an offender leaves behind clues.

"It's not a question of whether they'll be apprehended," Pitt said, "it's more a question of when."