Muchnick, who'd been in the Marines for about three years, had served in Afghanistan and was considering returning to college after his enlistment was up. He played high school lacrosse and football in Westport, Conn., and later played lacrosse at Eastern Connecticut State University, where he studied business.
"Roger was such an amazing person as he consistently lit up a room with his smile. He was charismatic off-the-field, and hard-nosed and tough on the field. He will truly be missed," Justin Axel, head men's lacrosse coach Eastern Connecticut State University, said.
In a biography on the university's website, Muchnick said the one thing he would like to do before he died was "live," and his most embarrassing moment was getting caught lip-synching in a school talent show.
"He was at the top of his game when this happened," said his grandfather, Jerome Muchnick. "You can't imagine losing a very handsome, 23-year-old grandson who was vital and loving."
Funeral services haven't been announced.
The Marines killed on Monday night were based at Camp Lejeune, N.C. The explosion's cause remains under investigation.