Burn his arse with a load of #4 steel shot at about 35 yrds or so depending on barrel length and choke. With longer barrels and tighter chokes you'll want to let some velocity spill off and get a good pattern spread. If you have a shorter barrel such as an 18" with an open choke, 20-25 yrds is enough distance. Just make sure that when you shoot, their head is turned away.
We do it all the time to dumpster diving brown bears out here and they seem to get the message.