I would say more of a robber/car jacker than mugger. Because he robs the manager of the wrestling venue. As he exits the building he pass Parker as he get on the elevator. When he gets outside, he car jacks Uncle Ben. At which point he kill him. Parker/Spiderman catches up with him at the warehouse. During the battle the robber/car jacker goes out the window on his on accord, as Parker/Spiderman watches.
It been a long time since I read any of the Spiderman comic book, so I don't remember Sandman's origin. He is a different person thou.
They did make some changes in the third movie, that is different in the comic book and the cartoon. The black suit is a suit in the movie both was never a real suit in both the cartoon or comic. But a alien entity, I am assuming it is an alien entity, but not sure why they put it in a box.