It sounds like he is decompensating pretty rapidly from the depression with the weight loss, crying, and not showing up for work. You probably do need to tell someone in a higher position at work. With his behavior/symptoms getting worse, they are going to notice anyway. Then it may come back to you in the form of 'you were the only one who knew, why didn't you say anything so we could have helped him before things got this bad?'
Hopefully there is someone very understanding at work who you can tell, someone who will work with him to get him the help he needs while protecting him from losing his job.