Originally Posted by Rommel49
I'm not sure the plan was necessarily to try and kill both of them with the fence, but rather to have the bandits kill Lee and mark by keeping them pinned on the other side of the fence (which almost worked). The family would've been able to make a far more credible excuse that it wasn't their fault if Mark and Lee were killed by the bandits (nobody else would know the fence came on just before the attack), and could also motivate the rest of their group into trying to get revenge on the bandits themselves which would take the bandits' attention off the Dairy.
I doubt it's a coincidence that Danny suggested trying to find the bandit camp and having everybody "mount up for some revenge" after the bandit attack, because no matter how a conflict between Lee's group and the bandits went, the St. John's would be the ones to benefit from it.
Later on while you tussle with Andy, however, you can shove him into the electric fence and it doesn't kill him outright. (He says 400 volts are pushed through it, but nothing about the amount of amps, so I'm not quite sure exactly how deadly it is). I think he planned to turn on the electric fence to injure one or both of Mark and Lee, to then justify "helping them" (no doubt the same way they helped Mark with the arrow in his shoulder by chopping off his legs
). I think it was a coincidence that the Bandits showed up at that exact moment, out of anger that their food was disappearing (thanks to Jolene, as we can guess from her video). They seem genuinely surprised that the Bandits are attacking them, and it is the first mention of their "deal" to give them food for safety.