Tyson wasn't technically a threat to Chole. Dean was working with Nia and Nia in turn was helping him by giving him money for his daughter's(Chloe) medical bills. Tyson and Dean met when Dean was going to the locker to pick up the money from Nia. Then later they show him and Wesley getting arrested and taken to the police station. At the station he sees that Dean is a "dirty" cop. So Dean is the one that got him off when Wesley had to do some time. Wesley then accuses him of snitching to get off so Tyson tells Dean that Wesley wants to kill him and asks for his help. Dean refuses so Tyson threatens to tell Wesley that Dean got him off and that's how it started. Dean strangles him and then puts him in that bag but Tyson is still alive and eventually comes to and tries to get out the bag. At that point Dean shots him.