A SeaTac man was sentenced Friday in U.S. District Court in Seattle to 15 years in prison and 15 years of supervised release for sex trafficking through force, fraud and coercion.

Ronnie Leon Tramble, 29, will also have to pay restitution to five women he forced to work as prostitutes, according to a media release from the U.S. Attorney’s Office. The amount of restitution will be determined at a later hearing.

Tramble first came to the attention of law enforcement in 2010 when Kent Police officers encountered a juvenile female working as a prostitute. The girl told police how Tramble beat and coerced her, and how he advertised her as a prostitute on Backpage.com.

“So many of these victims were juveniles and vulnerable,” U.S. District Judge John C. Coughenour said at the sentencing.

U.S. Attorney Jenny A. Durkan promised to keep going after criminals similar to Tramble.

“Sex trafficking is a horrific crime, that often preys upon our most vulnerable citizens: young children and teens,” Durkan said. “We will continue to target people like Ronnie Tramble who victimize our youth. Our community is safer with this defendant off the streets.”

According to court records, Tramble coerced or forced more than five different women to work for him as prostitutes. Some of these victims were under the age of 18. The plea agreement details how Tramble recruited one victim, and forced her to work as a prostitute with threats and violence.

Tramble repeatedly beat the victim, and forced her to give her prostitution earnings to him. Tramble was charged federally in August 2011.

After Kent Police initiated the case, further investigation by law enforcement revealed that for more than five years, Tramble forced numerous women to work for him as prostitutes. He has a prior Washington State conviction for promoting prostitution.

In their request for a significant sentence, prosecutors described the horror experienced by those preyed upon by Tramble.

“The seriousness of Tramble’s crimes is magnified by his constant physical, emotional, and verbal abuse towards his victims,” prosecutors wrote in their sentencing memo. “Each of the young women told chilling tales of being viciously beaten by Tramble and being threatened with even greater harm if they did not follow his rules. Victim T.E. spoke of being subjected to some of the most degrading acts imaginable – including being forced to have sex with Tramble against her will, and being forced to strip naked to prove that she was not hiding her prostitution earnings on her body. Tramble continually and horrifically exploited his victims for many years.”

Under the terms of the plea agreement, Tramble will have to register as a sex offender.

The case was investigated by the FBI’s Innocence Lost Task Force, which is composed of local, state and federal law enforcement officers who investigate juvenile prostitution. Key assistance was provided by the Kent Police.