Razor wire on top of the fence? If it's chainlink, hook a battery to it.....
Build watch towers and station armed sentinels
On a serious note, my wife would be flipping out. I would feel real uneasy about it too as I'm sure you are. I think the best thing to do is if you see him around again, make it known you are watching and know what he is up to. Also that you will do ANYTHING to protect your family and property. Good luck.
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