BOSTON (AP) — A Boston man will serve 30 years in federal prison for operating a large-scale sex trafficking ring that forced teens and young women into prostitution through intimidation and preying on their vulnerabilities.

Twenty-eight-year-old Raymond Jeffries was sentenced Thursday in Boston federal court and ordered to undergo sex offender counseling.

Jeffries' sentencing concludes an investigation into what was described as one of the biggest and most violent sex trafficking rings prosecuted by the U.S. Attorney's Office in Boston during the last decade.

At least 20 women, some teenagers, were forced into prostitution by Jeffries in a number of states from 2006 until May 2014.

Prosecutors say Jeffries also pleaded guilty to charges that he ordered a hit on a partner that he believed was cooperating with authorities. The victim survived.