Let's suppose for the moment that you're an evil person bent on committing a great atrocity. Specifically, you've taken it into your head to kill as many as possible of the hundred or so people packed into a small wooden church.
- A pickup truck with half a tank of gas
- The clothes on your back
- A $20 bill in your pocket
Improvise. Keep the budget in mind (so, e.g., buying a gun and a pile of ammunition is Right Out).
Even the lowest-grade homicidal idiot can surely come up with at least one workable plan of attack while falling-down drunk. And the really obvious attacks (given these constraints) can't be foiled by an armed bystander once the threat becomes apparent.