Ok, before anyone asks what happened to J, two dice were rolled with a random number generator.
The first dice was to see if J would be shot, a 30% chance of someone snapping and opening fire, a d100 dice was used.
The second was a d13 to randomly determine who would be the shooter, who snapped.
As you can see in the photo, a 74 was rolled on a d100, meaning someone snapped. The list that the shooter was chosen from was the list in the game thread's first post, so in this case, 1 meaning MtMerrick.
Hope that makes sense.