The back story is pretty minimal.
Punk kids were making a skateboarding video at a church in Gilbert, Arizona.
Gun guy decides he does not like punk kids skateboarding at the church and confronts them, telling them to leave.
They were like no, if you want us to leave call the cops. Gun guy drives around the parking lot, parks for a minute, then you see what was on the video. The punk kids take their stuff and leave in a vehicle. Gun guy follows them for a good while. The next day, the punk kids decided to call the cops themselves. The church had the video and it turns out that the gun guy wasn't even a member of the church. He just decided to teach those punks a lesson.