Jenelle Evans and her on-again fiance Gary Head are both behind bars, a source tells Us Weekly -- Head for domestic violence, and Evans for drug possession.
Teenmomtalk.com reports the pair were partying with pals when they got into a heated argument. During their spat, Head "hit her numerous times."
Evans has also been arrested, for possession of an illegal substance. If charged with assault, Head, a Marine, faces serious jail-time, and will most likely be dishonorably discharged from military service.
In April, the mom to Jace, 2, accused her then ex-boyfriend of getting physical during an altercation, though she didn't press charges at the time. The MTV star tweeted that she did "call the cops," but "told them I didn't want to press charges to jeopardize his career."
By early May, the pair had reconciled -- and on May 16, Head popped the question to Evans with a diamond sparkler.
Tweeted Evans, "I'm the luckiest girl in the world to have Gary Head in my life."