Why did Mr. Loomis shoot Edward? What does the shooting say about Mr. Loomis' character?

Edward continually asks to use the suit, so he can safely look for his family. Mr. Loomis, however, is afraid Edward won't return once he has the suit. When Edward puts the suit on.... Loomis kills him. From this, we can infer that Loomis is both self-centered and frightened.