My neighbor is moving and their trailer is parked pretty sketchy. Should I say something?

I really want to just go put something under the wheels but I've never talked to these people.

Update edit: thank you for all the replies. I went over and knocked but no answer. It's definitely not chocked. If I see them come home I'll go back over. I'm worried as soon as the weight shifts loading it that it will just go down the hill.