PHOENIX, AZ – Phoenix police arrested a suspect in the fatal shooting of a man who was operating a state police photo radar unit that was parked on a north Phoenix freeway to catch speeders, police said Monday.

The suspect was being questioned Monday morning, Phoenix police spokesman Sgt. Andy Hill said in a news release. Police said more information would be released at a briefing later in the day.

The victim, 51-year-old Doug Georgianni, was shot just before 9 p.m. Sunday on the Loop 101 freeway and 7th Avenue.

Video equipment on the photo enforcement SUV, which is marked as an Arizona Department of Public Safety vehicle, showed a vehicle that was believed to have been used during the shooting. The driver of that vehicle was described as a man who appears to be in his 60s and has white hair and a white mustache.

Georgianni had worked for three months for RedFlex Traffic Systems Inc. The company has a contract with DPS to operate photo enforcement vehicles and fixed cameras on state highways.

When he was shot, Georgianni was inside the Ford Escape and monitoring data collection, the DPS said.

DPS Director Roger Vanderpool called the killing “appalling (and) senseless.”

Before police announced the arrest, Redflex said it took its 40 radar vehicles out of service out of concern for the safety of its employees. “The entire Redflex family is grief-stricken for Doug and his loved ones,” Chief Executive Karen Finley said in a statement.

Scottsdale-based Redflex Traffic Systems is a unit of Redflex Holdings Group, based in South Melbourne, Victoria, Australia.

Arizona’s groundbreaking photo enforcement program is controversial, with state lawmakers considering legislation to eliminate the program when the contract expires in 2010. Meanwhile, critics have proposed initiative measures to put a repeal on the 2010 ballot.