枪朝他的肩部反冲过去。

The gun kicked his shoulder.

他弯下腰放下了他的枪。

He stooped and put down his gun.

这时，一支枪从他背后开火了。

Then, a gun opened up from his back.

There'd be certain activities perhaps, for example putting a gun to your head, that would put an end to your life.

也许会有某些特定的活动，比如用枪指着你的头，会结束你的生命。

because you're thinking the guy might be trying to steal your car, put you at gunpoint, hijack you,

因为你会想这个人可能是想偷你的车或用枪威胁你，劫持你，

It could mean "Shoot him, let him have it," or it could mean "Give him the gun, let him have it."

可以是说"开枪吧,给他一枪",也可以是说"给他吧,把枪给他"