A 9-year-old boy seriously injured when a tree fell on him this week at Hashawha Environmental Center in Westminster died Thursday morning at Johns Hopkins Children's Center in Baltimore, a Carroll County spokeswoman said. Vivian Laxton identified the boy as Noah Asid, one of two children injured when a 60-foot hickory tree fell as youngsters and counselors were preparing for a hike as part of the holiday-week nature camp. A 10-year-old girl was treated at Carroll Hospital Center and released. More than 60 children in fourth and fifth grades had been attending the three-day camp, which began Monday but was dismissed after the incident. Laxton said a county sheriff's investigation was under way.