As "they" say "looks may be deceiving". 3 out of 4 went off as planned. I don't think there are that many Americans who could get a bunch of malleable explosive, pack it, wire it, hook up the triggering device and set it off.
I'd bet a lot of kids growing up in the 40-50's could because they used to make their own "fireworks" with caps, black cats and M-80's... it's the trigger that might confuse somebody and kill them as they hooked it up.
at least that's what I've heard. ;-)
....well, what do I know? I never tried to make one. LOL