You are the recipient of a cultural flaw that has plagued our social institutions since the 1960’s: Teachers and Police Officers are expected to handle Psychological problems that confound trained Psychotherapists.
Please do not let shame or guilt destroy your heartfelt dedication to your students. If you came upon this former student drowning in a rain swollen creek would you notice that he’d been skinny dipping and walk away or would you jump into the swirling water to save him?
The shirtless messenger you encountered was likely drowning in his own mental disorder. Sending that message to an understanding person was his way of calling for help. If you had received training in how to handle people with mental disorders, you might have reacted differently than you did. Same case with the drowning nude swimmer. A trained lifeguard might have rescued the drowning swimmer without risk, but the lifeguard was not there and you were.