Luigi Mangione, who was arrested and charged with murder in the shooting death of United Healthcare CEO Brian Thompson, once belonged to a group of Ivy League gamers who played assassins, a member of the group told NBC News.

In the game, called “Among Us,” some players are secretly assigned to be killers in space who perform other tasks while trying to avoid suspicion from other players.

Alejandro Romero, who attended the University of Pennsylvania with Mangione and was a member of the same…