PHOENIX (AP) -- Authorities have formally filed charges against a man that police believe is responsible for sexually assaulting four women in Mesa and Phoenix and strangling two of them.

Trent Christopher Benson, 36, was arrested Wednesday afternoon by Mesa police at the Water-N-Ice store he operated.

Police also seized Benson's white four-door car saying it was impounded for examination in hopes of obtaining additional evidence, said Detective Steve Berry, a Mesa police spokesman. Police have served several search warrants in the case.

The most important thing was arresting Benson as quickly as possible so that he would not be responsible for any more killings, said Joe Shelley, a Mesa police commander.

"The work's just starting really," Shelley said, as detectives throughout metro Phoenix sort through unsolved murders and sexual assaults to see if they might be linked to Benson.

There has been no clear explanation why police believe Benson would have committed violent crimes after two previous arrests on prostitution-related charges in Mesa and Phoenix.

Police said they used DNA evidence to connect Benson to both crimes and two subsequent incidents, the strangulation of Karen Jane Campbell, 44, whose naked body was found in west Mesa on Oct. 14, 2007, and the Nov. 4, 2007 abduction and sexual assault of a 35-year-old Phoenix woman.

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Information from: The Arizona Republic, http://www.azcentral.com

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