Westmoreland would have turned 19 on Friday.
The school said in a release that the university was "deeply saddened" by the news.
"The Mississippi State Athletics Family is heartbroken by the sudden death of Sam Westmoreland," Bulldogs coach Mike Leach said via a statement. "Sam was a beloved son, brother and teammate, and a tremendous young man with a limitless future. He will always be remembered and deeply missed by everyone who knew and loved him. The entire MSU Family mourns as our thoughts and prayers go out to the Westmoreland family. Our highest priority is the support of the Westmoreland family and our student-athletes during this troubling time."
Oktibbeha County coroner Michael Hunt told The Associated Press Wednesday night that foul play is not suspected but did not provide further details. Mississippi State said that the Oktibbeha County Sheriff's Office and the office of the county medical examiner and coroner are gathering information on Westmoreland's death.
Westmoreland, a freshman, hailed from Tupelo, Mississippi, and played high school football at Tupelo High School. He was majoring in industrial technology at Mississippi State.
Westmoreland walked onto the Bulldog team after a decorated career at Tupelo High, where he earned a spot in the Northeast Mississippi Football Coaches Association All-Star Game last year. He also earned Region 2-6A second-team honors after his senior year in in 2021-22.
Mississippi State will be wearing helmet stickers during Saturday's game at Alabama in remembrance of Westmoreland. The Crimson Tide will also hold a moment of silence during pregame warmups.