They dug in and formed a defensive line as if 10,000 screaming North Koreans were going to burst out of the building at any moment, machine guns blazing.
Sickening.
Americans are not comfortable with friendly fire deaths involving children. The Israelis are a bit more lenient in that regard.
If the gunmen has been aware that there were armed people in the building, they may have deterred by that. The Virginia Tech gunman checked the classrooms for badges before he started shotting.