An 18-year-old man armed with a handgun was arrested after allegedly trying to steal merchandise from the Macy's department store at San Francisco's Union Square on Thursday evening, police said. The robbery was reported around 7 p.m. Thursday at the store near Geary and Stockton streets. The suspect, whose name was not immediately available, left the store with stolen hats and was confronted by an employee, according to police. The teen pushed the employee, a 59-year-old woman, and then fled, but was subsequently taken into custody and was found to have a concealed handgun on him, police said. The store employee was not injured in the incident.