will a 1000 fps pellet gun kill a squirrel?
Yes, BUT you need to be close, (with-in 50')and shoot for the base of the ear.
I've shot a bunch of rabbits with my air pistol, which is rated at about 550'/sec. BUT all of them were shots of less than 50', head shots only!
I say head shots because any thing other than that, the critters will get to a hole before they die!