The thief is using a battery powered angle grinder to remove the u-lock. The owner uses a key. The snipers will be well trained to distinguish between the two.

Hmm. Maybe this would be a good application of unmanned drones?

And what happens when an owner who lost his key gets shot for cutting his own lock?

We did that a couple of times with a mains-powered angle grinder and a mini generator. In the middle of the afternoon, in a shopping street. Got some funny looks, I can tell you. Nobody said anything though. Certainly didn't get shot.

Call me crazy, but I'm going to guess that the sniper suggestion was in jest.

Colateral damage. It also encourages owners to keep a spare key ... so it's not all bad.