COLUMBIA, Md. (AP) — The gunman who killed two people at a Maryland mall was a teenage skateboarding enthusiast who had no criminal record before he showed up at the shopping center armed with a shotgun, plenty of ammunition and a backpack filled with crude homemade explosives, authorities said Sunday. Darion Marcus Aguilar, 19, took a taxi to the Mall in Columbia in suburban Baltimore on Saturday morning and entered the building near Zumiez, a shop that sells skateboarding gear. He went downstairs to a food court directly below the store, then returned less than an hour later, dumped the backpack in a dressing room and started shooting, police said.