I don’t know what to do

So my building leaves packages in the lobby and they sort of pile them together. I had a bunch of packages arrive all in grey mailers. I grabbed them all. I didn’t realize until I opened a package that one wasn’t mine(it was sandwiched in the pile and looked exactly like the ones I had)

I ended up taping it up and leaving it on the persons door step. I just now realized while taping, the packing slip fell out. What do I do?