Dark comedy in 60s or 70s.
There was a comedy in the 70s about old people killing a bunch of people trying to develop their properties out from under them. I thought it had Ruth Gordon, but I couldn't find it on her listings. There was one scene where they put the person they had just killed in a concrete form as the concrete would be arriving the next day and his shoe was sticking out... the older lady just pulled out a hatchet and whacked it off. It was a really funny movie, but I don't remember the name. It was in color.
