How do I stop driving an entity (PAC3, I think?)

I have no idea how people can stand positioning with the Physgun.

Anyway, I held down C and right-clicked a lamp and clicked the “Drive” option. It let me control the entity as if I was a spectator. Perfect.

But now I have no idea how to stop driving the entity! How do I stop?

E?

[editline]17th September 2016[/editline]

Also standing with phys gun is pretty ez tho