That sounds like they're saying the border crossing to attack Israel at large was underway independent of any knowledge of the festival, but when they noticed the festival they diverted militants to attack it.

Booby traps are not legal and should stay that way because they are indiscriminate and could hurt people you do not intend to, including yourself.

Say you have a medical emergency and tragically die at home, and someone calls for a wellness check on you after weeks or months. If you have your house trapped for "protection," the first police officer that gets through the door ends up blasted by a rigged up pipe shotgun for no good reason.