S8·E12 Out of Sight; Missing Piece

After a night out with friends a college students prepares to go home as he is stabbed and killed. Once on scene detectives realize the violence in the area is growing, they come across a man being attacked. Could one of these men be the killer? Three teen boys have an argument, later one of them is shot in a backyard. Detectives set out to find out if these are friends or foe.