What about planting a bomb in his building but "hoping" that he survives?
Since the idea right now is pretty basic, you could discuss that you still have the thought of killing him.
I would approach it, by deteriorating the building. Start destroying outterouter parts of the building, maybe cut light/watter suplysupply, so that the building becomes unsafe and the best option is to demolish it. You would potentially have to raise a generation without telling them what is inside the building, so that they don't get any bad thoughts...