Children Shouldn't Play with Dead Things
(1972)
A small group of hippie college kids visits an island graveyard. Their freaky leader, Alan, has them dig up and party with a dead body named Orville.

Alan performs a half-assed satanic ceremony to resurrect the corpse. It fails, so one of the girls shows him how it's done. Unexpectedly, her ritual succeeds in raising the whole graveyard. Dozens of zombies slowly close in and eventually kill all the hippies. Orville personally kills Alan for making fun of him the whole time.

Final credits roll as the zombies pile on to the kids' boat and head for the mainland.

Thanks Don!