A photo-radar supervisor contracted with the City of Edmonton has been charged in connection with a case that shocked the city last week, when a woman was pulled over and sexually assaulted by a man police had thought was impersonating a peace officer.

Paul David Derksen, 50, was arrested Sunday and charged with kidnapping and sexual assault.

He is in custody and is due to appear in court on Wednesday.

Police said Derksen was contracted by the city's traffic safety section and worked as a photo-radar supervisor.

The Edmonton Police Service released this video of a man suspected of impersonating a peace officer in Edmonton. 0:19

Derksen, who was employed by the Canadian Corps of Commissionaires, was not charged with impersonation.

He was believed to have been wearing his "legitimate" uniform while driving home from work in his personal vehicle, a 2009 Nissan Rogue, early on Sunday, June 4.

"He wasn't impersonating a peace officer because he was a peace officer," deputy chief Kevin Brezinski said Monday at a news conference. "But certainly it's concerning for us and we utilized a lot of resources throughout the week to ensure that we came to a successful conclusion."

Victim saw flashing lights, pulled over

At around 2 a.m. on June 4, police said a man with flashing lights on his SUV pulled over a vehicle in the area of 91st Street and Anthony Henday Drive.

Dressed in a navy-blue uniform, the man got out of a white Nissan Rogue, identified himself as a peace officer and asked the woman to come back to his SUV.

He threatened the woman, police said, implying that he wouldn't charge her if she performed sexual acts on him.

The woman was driven to the area of Borden Park, more than 15 kilometres away, where she was sexually assaulted, police said.

The victim was eventually driven home, but not before she used her cellphone to secretly film her attacker.

"That was a critical piece of information that got us where we are today," Brezinski said.

Numerous tips from public

After news broke about the case, Edmonton police received numerous tips from the public that led to the arrest.

Police conducted a traffic stop on Sunday in the area of 39th Avenue and 97th Street, and said they arrested Derksen without incident.

Police released a photo of Derksen in case there have been similar incidents, Brezinksi said.

Gerry Shimko, executive director of Edmonton's traffic safety office, said Derksen had worked in photo radar operations for about three to four years.

He said Derksen was not on duty at the time of the alleged attack.

Shimko said Derksen is now suspended without pay, pending the outcome of the court proceedings.

Erosion of public trust

The disturbing case had police officers on edge, a former officer told CBC News on Monday, hours before news of the arrest broke.

Someone impersonating an officer can erode public trust in police and raise fears in the community, said Charlie Pester, a retired police officer and longtime traffic court agent in Calgary.

"The Edmonton police spokesperson said [the woman's attacker] is a top priority, but more importantly I think he's the priority of the officers on the street," Pester said in an interview with CBC Radio's Edmonton AM.

"That little video clip that the victim got was pretty good and that was a brave manoeuvre on her part," Pester said.

Pester said there were a number of warning signs in the details of the case.

Officers will rarely ask drivers to leave their vehicles, and would never ask them to sit in the front seat.

"If you're stopped in a run-of-the-mill traffic stop for a speeding ticket or a stop sign violation, normally the officer will just ask for driver licences, insurance, registration and go write the ticket," Pester said.

Drivers unsure of whether they've been stopped by a legitimate officer can take steps to protect themselves.

"If you get into a situation where you don't feel right, dial 911 and, if you're really uncomfortable, have them send a uniform car," Pester said. "And a real policeman, it would take him 10 to 15 seconds to figure this guy out. I don't think it would take very long to figure out a fake.

"This is a disturbing case," Pester said.