Or, you know, socialize healthcare :).
I don't see how anyone can be in favour of one, but not the other. In practice, though, most people favour one or the other, but not neither of both.
To most people, there is an extremely obvious distinction.
But those arguing for socialised medicine aren't arguing that society should help the gunshot victim, they're arguing that the money to do so should be coerced from members of society. That coercion is morally wrong, regardless of how worthy the recipient is.
Also, if societal support were voluntary, people could choose between supporting the gunshot victim or the bank.