A volunteer public safety group is patrolling parts of the city amid reports that two serial killers have been striking separately in recent months, killing as many as 11 people.

The Guardian Angels began their patrols in an east Phoenix neighborhood last week and expanded them to southeast Phoenix on Saturday. Some of the 16 shootings authorities attribute to the serial killers occurred in those areas.

Guardian Angels founder Curtis Sliwa said the new patrol area was crime-ridden even before the shootings.

"They're welcoming us and telling us horror stories related to drug-dealing, gang-banging and the prostituting that takes place here," Sliwa said. "They generally feel unsafe, so you add to it these serial killers, they're at their wit's end."

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He said many people in the neighborhood live in trailers without air conditioning and don't have a choice but to be outside in triple-digit heat.

"By being out there, that potentially makes them a target, and that gets them unhinged," Sliwa said.

Twenty-four unarmed volunteers will be divided between the two locations, and the group will discuss patrolling other areas, he said.

"We just want to keep the visibility up, make (neighbors) comfortable, give them a little relief," he said.

Sliwa founded the Guardian Angels in 1979. At the time, he was a night manager at a New York City McDonald's who was frustrated by rampant crime in the city. The group's first patrols were on subways and streets, and now it has 20 chapters around the world.

Sliwa traveled to Arizona on Saturday to determine whether the group had enough resources to sustain patrols through August. He said it does, but additional members were also expected to arrive from Chicago and San Francisco.

Sgt. Andy Hill, a spokesman for the Phoenix Police Department, said investigators have no problem with the Guardian Angels' patrols as long as members are careful and follow the law.

"It's really not significant to what we're doing," Hill said. "We just want them to be safe and get a hold of us if they have a problem out there."

One of the serial killers has been linked to a series of sexual assaults, robberies and six killings. The other has been definitively linked to the Dec. 29 wounding of one man, and authorities believe he could be responsible for five shooting deaths.