TACOMA -- Crooks who have masqueraded as police officers and kidnapped and robbed fast-food restaurant managers in the past month struck again Sunday, but this time, police say they've elevated their crimes to rape.

A Lakewood Wendy's employee was on her way home from work around 2:20 a.m. Sunday when she was pulled over by a vehicle with red-and-blue flashing lights, said Lauren Wallin with the Pierce County Sherrif's Department's CrimeStoppers program.

Two armed robbers handcuffed her boyfriend and placed him in the trunk of his car, then demanded her keys to the restaurant.

The woman didn't have keys to the restaurant, and after realizing this, the robbers took the victim into a fenced, wooded area in the 1900 block of E. 56th St. in Tacoma and raped her, Wallin said.

It's the fourth time these robbers have struck in the past month.

In all incidents, restaurant managers in Pierce County were pulled over by a vehicle with red-and-blue flashing lights shortly after closing and leaving their restaurant. Two unidentified suspects wearing bandanas over their faces then approached the victims' vehicle, flashed guns and handcuffed the victim.

In the previous three incidents, one of the robbers drove the victim back to the restaurant and forces the victim to unlock the doors at gunpoint, open the safe and give them cash.

The second robber then picks up the first suspect after the kidnapping and robbery, detectives believe.

The previous three kidnapping/robberies occurred:

• Sunday, Oct. 25, 2:30 a.m., Burger King on Mountain Highway in Graham

• Friday, Oct. 23, 3:15 a.m., Wendy's on Hosmer St. in Tacoma (attempted robbery)

• Monday, Oct. 5, 12:40 a.m., McDonalds on Steilacoom Blvd. in Lakewood

The men have used vehicles described as a dark newer SUV and an older black Honda with tinted windows, with red-and-blue lights on the dashboard. Both are described as white men, 20 to 25 years old, standing about 5-feet-8-inches, with a thin build.

During the robberies, the pair have been wearing dark hooded sweatshirts, dark hats, bandanas and gloves - and have been armed with handguns.

The kidnappings and robberies are being investigated by the Pierce County Sheriff's Department, Lakewood Police and Tacoma Police.

A reward of $1,000 is being offered for information leading to the arrest and charges filed for the robbers in this case. To contact police, call 253-591-5959. All callers will remain anonymous.