Story highlights Police arrest the 37-year-old officer

Investigation started last year after a woman complained about the officer

The alleged victims range between ages 20 to 47

A California police department is doing some soul searching after arresting one of its own on allegations of sexually assaulting half a dozen women.

While in uniform, a West Sacramento police officer assaulted at least six women since October 2011, police said Monday. The officer was fired, arrested and investigators are looking for other potential victims.

"I am just appalled and sickened that someone that was put in the position of trust would violate that trust in such an egregious manner," said Dan Drummond, chief of the West Sacramento Police Department. "The whole department is appalled."

Former officer Sergio Alvarez faces sexual assault and kidnapping charges, police said.

Alvarez, 37, worked at the West Sacramento Police Department since 2007.

A woman complained about Alvarez in September of 2012 and he was put on administrative leave. An investigation found six alleged victims, women ranging in age from 20 to 47, according to Drummond.

He released little detail about the alleged incidents because investigators are searching for other victims

The incidents occurred while the officer was on patrol and after he had stopped women who were walking, Drummond said.

He said some of the alleged assaults occurred inside a patrol car.

The police department has begun reviewing its practices such as allowing officers to patrol by themselves late at night.

"We are looking at our procedures and the way we are accountable to each other," Drummond said. "We want to make sure we are doing everything we can to make sure this does not happen again."