The Justice Department has utilized a federal hate crimes law for the first time against someone for targeting a victim based on their gender identity.

Yesterday, Joshua Brandon Vallum pleaded guilty Wednesday to violating the Matthew Shepard and James Byrd, Jr. Hate Crimes Prevention Act by killing Mercedes Williamson because she was transgender.

Vallum, a member of the Latin Kings gang, beat Williamson with a hammer, shocked her with a stun gun and stabbed her repeatedly, before hiding the 17-year-old's body in the woods near his house. Prosecutors maintain Vallum killed Williamson to hide their relationship from his fellow gang members.

Vallum initially told police he killed Williamson in a panic when he discovered she was transgender, he later acknowledged that was not true.

He has already pleaded guilty to murder charges and faces a life sentence in prison, but Vanita Gupta, head of the Justice Department’s Civil Rights Division, told Buzzfeed “it is important for us to send an unequivocal message that violence based one’s gender identity constitutes a hate crime. It is important for us to have spoken out on the bias motive.”

Williamson was one of 17 trans women of color known to have been murdered in 2015.

This year has seen the highest number of murders of trans people in America, and violent attacks continue: Just last month, Ralayzia Taylor of North Carolina was attacked by two men with a hatchet.

Passed in 2009, The Matthew Shepard and James Byrd, Jr. Hate Crimes Prevention Act adds sexual orientation and gender identity to the list of motives that qualify an act as a hate crime.