Do you have probable cause or reasonable suspicion?

You are patrolling at 2 am in June. You see a man standing on the side of a Subway sandwich shop that is open 24 hours. The man is peeking around the corner and he puts on a ski mask. The man sees your patrol car, removes the ski mask, and begins walking away from the Subway. Do you have probable cause or reasonable suspicion? Do you have justification to stop the man? Would you frisk the man? Write a short paragraph explaining what you would do and justify your actions?