A judge imposed a 17-year sentence Friday in connection with two violent carjackings of delivery men in Northwest Washington, authorities said.

Cephus Hollis, now 18, participated in the severe beating of a Washington Post delivery man and days later attacked a food delivery man he called to his home in 2014, according to a press release from the U.S. Attorney’s Office for the District of Columbia about Hollis’s sentencing.

A jury found Hollis guilty on 15 charges in November. The charges included assault with intent to kill while armed, armed carjacking and aggravated assault of a senior citizen while armed, the release said.

The release said prosecutors sought a significant period of incarceration, noting the “gruesome nature of the attacks.”