You are called by police to respond to a downtown street corner for an unresponsive man who is bleeding. you arrive and note that the police are already at the scene. lying face down on the corner is a​ disheveled, unresponsive man who appears to be in his 60s. as you​ approach, the officer tells you that he knows the individual as a homeless man who frequently panhandles in the area. the victim then begins to vomit bright red blood. what is your first treatment​ priority?