One of the hardest conversations I'm about to have

At work we are a very close knit community. Three out of the six of us have worked together for 5 years. We're starting to be concerned about the attitude and actions of one of us. We're afraid that he's become an alcoholic. I'm not sure of the classic definition of an alcoholic, but drinking is starting to affect his job performance and his quality of life. When he hasn't been able to drink for a period of time, he becomes intolerable to those around him. He'll start drinking early in the day, and alone. He has been showing up late. He has been belligerent to people in the office, and they have asked question. His drinking has put himself in danger, and has endangered the lives of others. This will not be pleasant, but it is something that has to be done in order to get him the help he obviously needs. I just hope he takes it well.