How would you handle neighbors that continually leave small dog poop piles on a shared lawn?

There are some folks that live around me in our HA that think they are above picking up their dogs pile of excrement. I’ve bagged it up myself and taken it to their front porch, their car door, their car roof and now finally their door mat. If I step in another pile of shit I think I am going to go insane. I’ve called the housing authority and the managers but without proof of which dog(s)/owner is doing it they won’t act.