Michael's bodyguard shows up at Roth's hotel room in order to kill him. He first must dispose of Ola whom he dispatches with a coat hanger. He didn't use a gun or knife. Why not? Of course, a gun makes noise and attracts attention. Perhaps it was a challenge to get a gun in Cuba or to acquire one after arriving there and also to acquire a silencer. So, why not a knife? One of those is easy enough to obtain.

Also, what about Ola's body? Why didn't Roth's entourage find it? Why didn't they notice him missing?