A 14-month-old boy--injured when a plane crashed into a crowded Concord shopping mall--has died, becoming the fifth victim of the accident last Monday. Alexander Luong, of Concord, had suffered second- and third-degree burns over 35% of his body. Besides the baby, the crash took the lives of the plane's pilot, his two passengers and a shopper. Injured were 76 people and 16 of them are still hospitalized, six in critical condition. The Beechcraft Baron plunged through the mall roof and sent down a shower of flaming debris on shoppers. Investigators have narrowed the cause to poor weather or pilot error, experts of the National Transportation Safety Board said.