Authorities gave no details about why they believe Dale S. Hausner and Samuel John Dieteman are responsible for the three dozen shootings investigators had labeled as the work of the "Serial Shooter," or whether they believed both men or just one pulled the trigger.
The attacks, which began in May 2005, left six dead and were all the more frightening because another, apparently unrelated serial killer has been preying on Phoenix-area victims at the same time.
At a news conference Friday, authorities said they were confident they had the right suspects.
"These are the two monsters we have been hunting, and I promise you and our colleagues promise you, we are not finished," Phoenix Mayor Phil Gordon said.
Hausner, 33, and Dieteman, 30, were arrested late Thursday in an apartment complex in nearby Mesa. Neighbors said the men shared an apartment.
Police Chief Jack Harris said the suspects will face numerous counts of murder and aggravated assault, though authorities did not have specifics on how many.
Hausner and Dieteman were being interviewed at police headquarters Friday afternoon but had yet to be booked, a police spokesman said. An initial appearance had not been set.
Police said Friday morning that they knew nothing about the suspects' occupations, but neighbors said Hausner worked as a janitor at the Phoenix airport and as a freelance photographer.
An Internet search Friday turned up several photographs taken by Hausner of women boxers. A Web site offering his services as a wedding and party photographer displays his boxing photography work, as well as picture of him shaking hands with Mike Tyson.
Jill O'Donnell, 20, who lives in the complex near Hausner's apartment, said she spent considerable time chatting with Hausner, but added that during the last month, he wouldn't say hello or wave when she passed by.
He "seemed like a really nice person, but he gave off a vibe of someone you didn't want to be too social with," O'Donnell said.
Dieteman said nothing the one time they met while inside the men's apartment, she said.
Knowing the suspects "brings a whole new level of terror," O'Donnell said.
Investigators searching the apartment complex Friday morning used flashlights to peer through the windows of a car, which was later hauled away by a tow truck, and television footage showed police carrying what appeared to be several rifles or shotguns away from the apartment.
The Serial Shooter targeted pedestrians and bicyclists on empty streets throughout the Phoenix area. Twenty-three people were shot, six fatally, and even horses and dogs were among the victims.
"I hope they got him," said Caroll Roberts, whose 19-year-old son was shot in the torso last month and survived after four hours of surgery. "I want to shoot him in the stomach to see how he'd like it, like he did my son."
Assistant Police Chief Kevin Robinson said the crimes appear unrelated to the still-unsolved "Baseline Killer" cases: eight slayings and 11 rapes since August 2005. Investigators are scouring the city's trove of unsolved crimes for links to the serial predator and clues that might help police catch him before he strikes again.
The two serial-killer cases doubled the fear and paranoia gripping Phoenix neighborhoods in recent months, and led law enforcement agencies to devote more than 200 investigators to track down the killers. Authorities said they will move investigators from the Serial Shooter to the Baseline Killer case.
Robinson described Hausner and Dieteman as friends who had no obvious connections to any of the victims.
"The best we could tell, they were just random victims. These individuals just picked victims out and that was it," Robinson said.
Police would not discuss what tipped investigators off, or what they thought the men's motives were.
Authorities said they tracked Hausner and Dieteman closely after identifying them as suspects Monday evening, but would not discuss the evidence that led to their arrests.
"It wasn't just one source," Robinson said. "We were able to get on these individuals from a lot of different sources."
The most recent shooting in the case occurred Sunday in Mesa, less than three miles from Hausner and Dieteman's apartment. Robin Blasnek, 22, was killed as she was walking from her parents' home to her boyfriend's house.
Tom Mangan, a spokesman with the Bureau of Alcohol, Tobacco and Firearms, said that Hausner and Dieteman also are believed to have committed arson.
Mangan said ATF investigators had spotted two people who looked like Hausner and Dieteman in surveillance video from two Glendale Wal-Marts that had been set on fire in June.