One of the bar's co-owners said both groups were kicked out and that no punches were thrown inside the bar.
However, police said Lopez was unconscious when they arrived. He was airlifted to Denver Health Medical Center and was pronounced dead Monday morning.
The incident happened shortly after midnight Friday.
Police said they have interviewed several people but there have been no arrests in the case.
According to police, the suspects fled the area and hired attorneys.
Lopez was stationed at Fort Bragg along with one of his friends who was involved in the fight. A second friend, who was involved in the fight, is in the Navy. Both of the friends were injured in the fight.
All three of the men were on leave.