The serial shooter also attacks at night and preys on individuals who are walking alone or waiting at deserted bus stops. Less is known about the suspect, and no composite sketches have been created. The shooter is also accused of shooting animals and has been known to use a shotgun.
Police have reviewed video tapes recorded by security cameras at two different crime scenes. But very few details about either suspect have been released to the public -- leading many here to suggest that police are either worried about tipping off the killers and thwarting the investigation or that they've come up empty-handed.
The police department has turned down repeated requests for interviews with detectives, leaving it up to Mayor Phil Gordon to defend what appears to be an increasingly frustrated investigation.
"Certainly frustrated because out of professionalism," he told ABC News during an interview at his downtown Phoenix office. "These are officers that are community members -- they're fathers and mothers and sisters and brothers. And these two individuals are causing a lot of anxiety in this community and certainly with the national attention, it isn't what this city is about."
When pressed on whether the police investigation is stalled, Gordon became irritated.
"This is a safe city. It's a great city. It's growing," he said. "People have their entire families outside playing in the evening, during the day. Listen, I'm proud -- I live in the center of the city. I have a 7-year-old and he's out playing, but we watch our children just like any parent should."
But many others are not out at night. Phoenix is virtually deserted after sundown. Anxiety and paranoia have kept many off the streets.
Dana Gray, a financial analyst, is one of them -- and for good reason.
"I actually had the gun pulled on me," she said.
In December 2005, she was held up at gunpoint inside the gate of her central Phoenix apartment house. Now, with two serial killers on the loose, she's decided to take action.
"I'm here at the gun range because I want to learn how to shoot firearms. I want to feel safe," she explained. Gray is training for a "conceal carry weapons" permit, which requires several hours of classroom instruction and target shooting.
"Get out! Get out! Get out of my house! NOW! Get out!" she yells at the projected image of a burglar on a large video screen meant to simulate a residential break-in.
"I won't go out at night," she says after finishing the drill. "I once in a while walk my dog at night if that's necessary, but usually we take care of that before dark, and I just don't go out at night. I think more people need to do what I'm doing."
After firing a 9 mm pistol at a target several feet away, Gray's confidence seems to build.
"We need to even the score here a little bit," she said. "We need to start taking care of ourselves and learning to defend ourselves. And maybe as bad people know that this is happening they'll be a little less likely to approach people."
At a gun shop in Tempe, handgun sales are booming, but it's the mace and pepper spray that dealers can't keep on the shelves. During our visit, a man bought the last two canisters for his daughter and his wife. He explained his daughter worked the late shift at a bar and felt vulnerable just getting to her car after work.
Down the street a martial arts class was full. Dozens of young women and men yelled, kicked, punched and shoved one another using Israeli Defense Force training called Krav Maga. Jay Ackerman, the chief trainer, told ABC News "attendance has spiked" since the two serial murders began their crime spree.
"We teach aggressive street fighting. Your elbows, knees, and feet can be powerful weapons," he said.
The Valley of the Sun -- this urban oasis in the desert -- has become a city under siege. And in true Western style, its residents are fighting back.