Police blame two series of attacks in which 11 died on ‘Baseline Killer’ and ‘Serial Shooter.’

Summer nights used to be something to look forward to in this sweltering, sprawling metropolis.

Residents don’t dare leave air-conditioned homes and offices during the day, when temperatures routinely crack triple digits. When the desert sun goes down, parks fill up, joggers take to the streets and diners flock to outdoor tables at restaurants.

But this summer, it’s a different story. Phoenix is being terrorized by at least two serial killers who have killed 11 people, striking after dark. Residents across the city are thinking twice before going out at night.

“During the day you can’t do that much because it’s 115 degrees,” said Tene Burrow, 27, an elementary school teacher who lives near the site of one of the killings. “But for me right now, lay low. Do as little as possible, stay safe. Unless it’s something I have to absolutely do at night I’ll just stay in, and sweat it out during the day.”

The string of killings has startled a city of 1.4 million known more for golf, retirement homes and quiet living than for urban paranoia.

“It’s not a joking matter anymore,” Burrow said. “But it was like, a serial killer in Phoenix, Ariz.? Come on! This isn’t New York, this isn’t D.C.”

The attacks have taken place mostly across a 70-square-mile area of central metropolitan Phoenix. The area includes immigrant neighborhoods bursting with taco stands and auto body shops, and high-end streets fronting Scottsdale’s upscale apartment complexes. The victims, apparently chosen at random, include men and women of all ages. The killers used guns.

Police call one of the attackers “The Baseline Killer” after a broad boulevard that runs through poor neighborhoods and upper-middle-class suburbs where he snatched several of his victims. The killer, described by police as a black man who may use a disguise that includes a long-haired wig and a floppy-brimmed hat, has ranged far beyond Baseline Road. He has killed five women and one man ages 19 to 39, police say, and committed eight robberies and seven sexual assaults.

The first crime linked to the Baseline Killer was the September shooting death of a woman in her Tempe apartment complex parking lot. Police say he also killed a schoolteacher waiting for a bus in central Phoenix and two workers at a Chinese restaurant who disappeared after their late shift on March 15. Their corpses were found the following day.

The most recent victim was Carmen Miranda, 37, a mother of two who was carjacked June 29 at a carwash on a working-class stretch of Thomas Boulevard, one of Phoenix’s busiest roads. A surveillance video showed her being grabbed while she vacuumed her Ford. She was found dead in the car behind a nearby barbershop.

Police say the killer tries to initiate a conversation before attacking.

Police say a second killer, whom they have dubbed “The Serial Shooter,” has shot at least 22 men and women ages 16 to 56. Five have died. Police believe the shots have come from a light-colored, four-door sedan. Police do not know the shooter’s gender, and say it is possible that more than one person is firing from the car.

Since May 2005, the sniper has largely targeted people walking alone. But victims also include people getting off buses at the end of workdays, and riding or pushing bicycles. The sniper has also killed dogs on the street and is believed responsible for fatally shooting three horses on private property.

The Phoenix Police Department has assembled a 120-person task force to investigate the crimes and is working with the FBI and the Bureau of Alcohol, Firearms, Tobacco and Explosives.

About 4,000 people have called the department tip line, police say. More than 1,500 people crowded into an auditorium this month for a community meeting on the killings. The Guardian Angels, the volunteer crime-fighting group, began patrolling central Phoenix this week. The Police Department has started holding daily news conferences on the killings, although there were no developments to report this week.

“An investigation is like building a house,” Sgt. Andy Hill, a department spokesman, said at a news conference this week “You just keep putting each brick in there. You start slow but you get results.”

Hill said he was frustrated by media reports about Phoenix residents cowering in the face of the killings. “This is a community that’s on the offensive,” he said.

Margaret Ubauer certainly sounded that way as she stood outside a supermarket a few blocks from one of the slaying scenes. “Me and some other gals were thinking of getting some guns and looking for them ourselves,” said Ubauer, 61, who works with mental patients in a hospital.

But Ubauer admitted she doesn’t leave her house at night anymore and worries about her daughter-in-law, who works nights.

Bobby Kelly is concerned about her own late nights. A supervisor at the supermarket, she’s worked out a system with co-workers to have people watch each other at night as they pull into the parking lot and walk inside.

Kelly, a lifelong Phoenix resident, had never paid attention to stories of murder and mayhem on the news until the Baseline Killer attacked someone near her workplace. “It’s a whole lot closer now.”