I wasn't sure if this was a bug or if this is being caused by something that I'm doing wrong. I was pretty close to submitting this to the bug tracker but then I reconsidered since this may not be a bug (or maybe it is, I don't know).
Anyway, take a look at this:
Open the .cap and run the layout. Notice that when you shoot an enemy, it destroys all the enemies at once.
Now go to the event editor, remove the "enemy is on screen" condition (only the "enemy on screen" one, leave the collision condition alone) and run it again. Now the enemies are destroyed by your bullets one at a time, how it should be.
I'm puzzled though. Why does adding the event "enemy is on screen" make it so that it destroys all enemies? Is this a bug?
If it isn't, how do I make it check for whether each individual enemy is on screen? I thought it was automatically supposed to do that.