bullets don't hurt, but punches do?

lol, just watched the scene where Williamson and Roundtree are confronted by by vamps at Williamson's car. Roundtree shoots them and they aren't hurt at all, so he throws the gun away and the two guys beat the crap out of the vampires. Hmm, so they are impervious to bullets, but human fists and feet are enough to put them down ??? lol

Much love to Richard and Fred though.