A 17-year-old student is in critical condition after he was shot on the first day of school today in a Baltimore suburb and a quick thinking teacher subdued the teenage gunman, ABC News reports. The alleged shooter was another student who was 15, Baltimore County Police Chief Jim Johnson said. The suspect was arrested, Johnson said. The school, Perry Hall High School, was evacuated. The 15-year-old student, whose name was not released, walked into the school cafeteria at 10:45 a.m. and fired one shot, the chief said. A student described the weapon to ABC News affiliate WMAR as a shotgun. Police haven’t confirmed the type of weapon used. A teacher grabbed the boy with the gun and wrestled him against a wall, holding the gun away from the shooter. A second staffer, a school resource officer, was outside the cafeteria and rushed in to help the teacher subdue the suspect until cops arrived, police said…