SANTEE, Calif. -- A 20-year veteran of the San Diego County Sheriff's Department faces five felony charges for allegedly sexually assaulting a prostitute in Mission Valley while on duty last winter, officials said Friday.

Detective Thomas John Sadler, who is assigned to the agency's Lemon Grove substation, was arrested at his home Thursday afternoon by investigators with the San Diego Police Department Sex Crimes Unit, SDPD Capt. Jim Collins said.

"Obviously, it's very disturbing to all law enforcement," Collins told reporters during an afternoon briefing.

Sadler, 47, is charged with one count each of sexual battery by restraint, assault and battery by an officer, and false imprisonment by violence, menace, fraud or deceit, along with two counts of accessing a computer to defraud.

The Santee resident, who faces nearly seven years in prison if convicted of all the charges, posted $250,000 bail and is scheduled to be arraigned next week.

According to a declaration filed in support of an arrest warrant, the prostitute, who is in her 20s, was sitting on a curb in the 3100 block of El Cajon Boulevard in the North Park area of San Diego when Sadler, driving his unmarked work vehicle, pulled up alongside her about 10:30 a.m. Feb. 6.

"As far as we know, he had no official business in that area," Collins said.

Sadler allegedly identified himself as a "sheriff's officer," forced the woman into the Ford Taurus and drove her to the 2800 block of Camino del Rio South, where he pulled over on the edge of a restaurant parking lot.

Sadler then reached under the woman's skirt and forcefully fondled her before pulling her bra and white tank top up and groping her breasts, the declaration alleges.

Once allowed out of the vehicle, the woman attempted to take a photo of the car's license plate, but Sadler prevented her from doing so by grabbing her cell phone and "disabling" it, according to the affidavit.

Three witnesses saw the alleged altercation, and each called 911 to report what they took to be a kidnapping in progress. Sadler fled before police arrived, according to the court filing.

About three hours later, Sadler allegedly accessed a department computer system used to check for wanted persons and vehicles and looked up his assigned county vehicle and the address where the alleged assault took place.

Six days later, the prostitute called San Diego police Officer Wendy Valentin, telling her that she had seen Sadler again behind the wheel of the same Ford sedan and took down the license number.

Sadler, listed as being assigned to that Sheriff's Department vehicle, was contacted but refused to make a statement, Valentin said.

The next day, the alleged victim, whose name was not released, and two of the witnesses positively identified Sadler as her alleged assailant, picking him out of a photo lineup, police said.

The Sheriff's Department has put the suspect on unpaid leave pending the outcome of the case, a spokesman for the county agency said.

Collins said the investigation took nearly six months to complete because detectives had to uncover "as much detail as we could to corroborate the (accuser's) story. And then the District Attorney's Office had their process of reviewing it."