A company in Minneapolis is making products to protect schools in the event of a shooting.
The Aaron Carlson Company's 'Safe Schools, Safe Kids' division has developed a line of bullet proof doors and windows that are designed to stop rounds fired from a wide variety of weapons.

The company's president says traditional doors and windows do nothing to protect against a shooter.
Jason Horner, president of Safe Schools, Safe Kids, said : "They can shoot the glass out of a door, walk right through the door, reach through and unlock the door, giving people on the other side of the door very little time to react."
These bulletproof doors are not cheap.  One model of door that is designed to stop an AR-15 round will cost about $10,000.