Help!! Does anyone know this movie!?

a movie about where people are in an elevator and the power keeps goin out and everytime it does a person is killed , theres an old grandma that is doin the killing, that they thought was dead because she was the first to die becuase she was hung and the black guy is wearing a uniform that says calaway security and of of the guys in the elevator said over the walkie talkie that he had killed a mother and child 5 years ago in a hit and run.