KPNX-TV and The Arizona Republic reported on the arrests, which took place at a gated apartment complex in Mesa late Thursday.
Authorities identified Dale Hausner and Samuel Dieteman as those responsible for the "Serial Shooter" case, one of two serial killers thought to be operating in the Phoenix area. The Republic reported that numerous tips from the public led police to the suspects.
"They are the serial shooters that this task force has been hunting," Phoenix police Chief Jack Harris said at a press conference Friday morning.
"These are the two monsters we have been hunting, and I promise you and our colleagues promise you, we are not finished," added Phoenix Mayor Phil Gordon.
The series of shootings, which began in May, 2005, have killed six people and left 18 wounded.