A Long Beach man who worked as a security guard was sentenced today to 30 years to life in prison for sexually assaulting more than a dozen women—often at gunpoint—over the span of four years, according to the Los Angeles County District Attorney’s office.

Ferdinand Ervin Flowers, 36, targeted sex workers he’d pick up along a railway corridor leading to the Long Beach-Los Angeles port complex, authorities said.

He would usually find them in South Los Angeles where he’d talk them into the car or truck he was driving, according to prosecutors. He’d then rob them, drive to a remote industrial area around Compton or Carson and sexually assault them, according to authorities.

Prosecutors said he’s responsible for attacks on 13 victims between Jan. 30, 2014 to Jan. 12, 2018.

Long Beach Security Guard Arrested for Kidnapping, Sexually Assaulting 14 Women

As part of a negotiated deal with prosecutors, Flowers pleaded no contest in September to two felony counts each of forcible oral copulation and assault with intent to commit forcible oral copulation.

He also admitted to using a handgun and agreed to pay restitution to all 13 victims, the youngest of whom was 15, according to authorities.

Investigators discovered the pattern of his attacks after using DNA to link the crimes, according to authorities.

Police arrested Flowers in January after detectives saw a 19-year-old woman get out of his car near where other victims had been dropped off, they said.

Prosecutors credited the victims with helping investigators break open the case.

“It was a hard thing for these women to come forward,” Deputy District Attorney Frank Dunnick said.

Los Angeles Superior Court Judge Joel Wallenstein, who handed down the sentence in a Compton courthouse, also ordered Flowers to register as a sex offender for the rest of his life.

Jeremiah Dobruck is managing editor of the Long Beach Post. Reach him at [email protected] or @jeremiahdobruck on Twitter.