Many states have ‘make my day’ laws. They do not allow deadly force to be used unless fear for life is involved, and some do require a retreat if possible. These students knew they were police officers entering, and it would be very hard for them to claim they feared for their lives. They might have feared being arrested, or feared their property might be removed (the source of the music), but I’d have a hard time believing they were fearful the cops were there to take their lives.