A Stockton man police said shot and killed a Santa Rosa masseuse at her office near downtown may have had a history of raping and robbing women in Northern California, authorities said Tuesday.

John Quincy Ellis, 46, committed suicide Feb. 6, the day after he killed Carole Marie Brooks, authorities say. As police tried to apprehend him, Ellis ran into the path of a big rig on Interstate 5.

At the Stockton home Ellis shared with his ex-wife and two children, detectives found evidence linking Ellis to the January rape and robbery of a woman in San Francisco and other items that indicated he was fascinated with rape, Santa Rosa Police Sgt. Steve Fraga said.

"There's no doubt in our minds that John Quincy Ellis was the suspect in our case," San Francisco Police Sgt. Michael Andraychak said.

Detectives searching Ellis' home found a suitcase filled with handcuffs, rope, tape, a mask and pornographic videos, Fraga said.

Crime books detailing prior cases of serial rapists were "strewn throughout his bedroom," Fraga said. "Then he's responsible for a murder in our town, and he's responsible for a sexual assault robbery in another nearby town.

"That's the reason why we have reached out to all law enforcement agencies to tell them what our case is all about."

Fraga said Ellis exchanged text messages with Brooks, 60, on Feb. 5 before he arrived at her Clark Street studio, police said. They had arranged an appointment, possibly for a massage.

However, within moments of Ellis' arrival he shot Brooks in the abdomen and fled. Brooks died later that day at Santa Rosa Memorial Hospital after telling police a man she knew as John Paul had demanded money and then shot her, Fraga said.

Multiple witnesses who heard the shots noted part of the shooter's license plate as he drove away, and detectives later found Ellis through his rental car.

In searching Ellis' home, detective found items that had belonged to the woman who had reported being raped and robbed in San Francisco, Fraga said.

The 49-year-old San Francisco resident was assaulted at about 2:20 p.m. on Jan. 22. in San Francisco on 23rd Street near Kansas Street, San Francisco Police Sgt. Michael Andraychak said.

She was not identified because she was the victim of a sexual assault, and Andraychak would disclose no more details about the case.

However, he said the sex crimes unit "closed our case as a result of information gathered through our investigation as well as the information obtained from Santa Rosa."

Stockton police and Sacramento County sheriff's detectives are investigating whether Ellis may have been involved in similar unsolved cases in those jurisdictions.

Details about Ellis' possible M.O. were still unclear, including whether he targeted women who advertised sexual services online.

Brooks had posted several ads for sensual massage on a website used by people advertising erotic massage, escort and other sexual services.

Ellis had several log-in handles associated with the same website, Fraga said.

Santa Rosa detectives suspect Ellis may have demanded sexual services from Brooks in the brief moments before the shooting.

"I think he wanted something other than a massage, and I don't know that he was willing to pay for it — that's a theory," Fraga said. "And it sounded like she wasn't game for that, and that led to a confrontation."

Several witnesses initially told police they believed they had seen Ellis visiting Brooks before but were later unable to identify him from a photograph lineup.

Santa Rosa detectives will close their inquiry into Brooks killing once ballistics lab results confirm whether a revolver at Ellis' house was used in her shooting.

"Our case is rock solid, it's done," Fraga said.