A serial rapist has victimized more than 30 women as they worked as massage therapists in a three-county area, according to Riverside police now seeking the public's help in identifying him.

The assaults date back to 2009. But only recently have DNA matches enabled police to link individual cases to the same perpetrator, said Riverside Police Officer Javier Cabrera. The perpetrator has displayed a handgun.

"He gains access to the business, and once inside the business, that's where the sexual assaults occur," Cabrera said.

Besides Riverside, attacks have also occurred in San Bernardino County and in Los Angeles County in the east end of the San Gabriel Valley, according to Cabrera.

Investigators released Wednesday morning still and video images of the perpetrator from security camera systems in several of the massage businesses, pictured below.

A Riverside police detective called the string of attacks "repulsive," and detailed one particularly violent encounter between a victim and the perpetrator.

He "chased a 55-year-old woman down a hallway, slammed her into a wall dislocating her shoulder, breaking her collar bone, knocking out five teeth. He began punching her, then he drags her back down the length of her hallway by her hair," Detective Aurelio Melendrez said.

"So, he's capable of great violence."

Police were investigating whether the perpetrator in another attack on a masseuse in Riverside was the same serial rapist linked to the string of assaults. They determined that attack was not part of the crime series.

In that case, a masseuse who operates her own business in Riverside on Hole Avenue has twice been victimized by an intruder, said property owner Darrell Clardy. The woman was bound and placed in a room, but was able to escape.

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