An armed man who took about 100 students and teachers hostage Thursday at a school in north Teheran surrendered and his captives were released without injury, official news agency IRNA reported. The man surrendered to police forces at the Razi boys' secondary school about two hours after taking the hostages on Thursday morning, the agency reported. It was not clear what the gunman had demanded, but it appeared to be a personal dispute. The man was looking for a teacher working in this school, witnesses said.