First get a carepackage then put it anywhere. When the carepackage has landed leave it and find a good spot to see the care package.

When you see them running to it, they won't notice you and you can kill them.

If you see 3 people at the carepackage you can just shoot them and wait for the other ones to come to your carepackage.

So basically it's like a monkeybomb, but the carepackage doesen't explode.