quarantine 'em

* Burns is shot at 3pm (he mentions the time in dialogue and then a bell is heard tolling) * Smithers says "I never miss 'Pardon My Zinger'" * A television ad in Moe's earlier in the episode indicates that this show airs at 3pm * Cast-iron alibi

These observations rule out the two primary suspects. So who did do it?

* During the town hall meeting, Burns shows that he is carrying a gun to protect himself. * But when he collapses, for one frame it can be seen that his shoulder holster is empty. * Burns has lost his weapon and was most probably shot with it.

(Several of the suspects did not have access to a firearm. Unfortunately, this clue places them back under suspicion.)

Burns collapses with his hands pointing to the letters W and S on the town sundial. This suggests that the assailant had the initials M. S., S. M., S. W. or W. S..

(Analogue clocks set to 3 o'clock and 9 o'clock throughout the episode have been training us to think about looking at the sundial upside-down.)

It is possible that "S. W." indicates "Smith & Wesson", Grampa's gun which is seen earlier, and to which numerous characters have access - but only one shot was heard, and we already ruled this firearm out, above.

At this point in The Simpsons' run, there are several characters who definitely had these initials (and who appeared in this episode): * Waylon Smithers * Marge Simpson * Moe Szyslak (his surname was revealed for the first time in this episode) * ...