AUGUSTA, Maine -- A former U.S. Marine has been sentenced to serve four years in prison after pleading guilty to causing a June 2012 car crash that killed his sister and the woman's boyfriend.

Travis Lawler was on leave from Camp Lejeune in North Carolina when the car he was driving went off a road in Belgrade, Maine, and struck a tree.

Twenty-year-old Kristin Lawler died at the scene and 25-year-old Jackson Bolduc died from his injuries the following day. A third passenger sustained serious injuries.

The Kennebec Journal reported that Travis Lawler, in full Marine dress uniform, sobbed as he pleaded guilty to charges including manslaughter and drunken driving on Monday in Kennebec County Superior Court.

The 23-year-old Lawler said he was sorry and that he wished he had not gotten behind the wheel that night.