PHOENIX, Ariz. (AP) August 4, 2006 — Authorities arrested two men Friday in an investigation into a series of fatal shootings that have terrorized Phoenix area residents.

''We do have two suspects in custody,'' Sgt. Andy Hill told reporters Friday morning. ''They're at Phoenix police headquarters in the serial shooter case. A search warrant was served in Mesa last night.''

Authorities have said that the so-called ''Serial Shooter'' is believed to be responsible for killing six people and wounding 17 others, mostly pedestrians and bicyclists, since May 2005.

The most recent was Sunday in Mesa when a 22-year-old woman was fatally shot as she was walking from her parents' home to her boyfriend's house, authorities said.

Investigators were seen Friday walking out of the Mesa apartment complex with several firearms. Hill declined to release additional details about the arrests but said authorities had seized a vehicle in the case.

''It had nothing to do with a traffic stop,'' Hill said. ''It had nothing to do with information from a particular meeting.''

Fear and paranoia have gripped the Phoenix area amid reports that not one, but two serial killers have been striking separately in recent months.

Phoenix police have had about 200 officers working to try to solve the Serial Shooter cases and to find a second serial predator dubbed the ''Baseline Killer.''

The ''Baseline Killer'' is believed responsible for killing seven women and one man since last September, and sexually assaulting 11 women and girls in the past year.

Authorities have said that the so-called ''Serial Shooter'' is believed to be responsible for three dozen shootings of people, and dogs and horses. The shootings have generally happened late at night, with no witnesses.

Robin Blasnek, 22, was gunned down at about 11:15 p.m. Sunday. Neighbors heard a shot and ran to help the young woman, but she soon lost consciousness and died at a hospital.

The shooting was linked to earlier cases because of similarities and forensic evidence, authorities said.

Blasnek's father told the East Valley Tribune that his daughter grew up as a special needs child, and lived part time with her parents in Mesa and at a group home in Tempe.

''She was just a great kid. Very, very naive, and pure as far as not understanding the dangers of the world,'' Steve Blasnek said. ''I guess my only regret is that I didn't give her a big hug.''