YOUNGSTOWN, Ohio - Active shooter events in schools across the United States have tripled since just 2007.

Now, a Howland police officer has invented an easy way to keep students safe in their classrooms.

Schools are trained to have teachers barricade doors if there is an active shooter present in their schools, but that takes time.

Police officer and inventor Bill Barna said,"We saw they were following ALICE protocol, which is typically barricading the doors with desks and chairs. It's labor intensive and time consumptive. Time is of the essence. We know active shooter events typically take 10-15 minutes."

So, Barna, a Youngstown State University alumnus and substitute teacher, invented the BOLO stick. It's a steel plate secured against the bottom of a door with a small hole in the floor.

How does the BOLO stick work? All a teacher has to do is close the door and drop a solid steel pin through the hole. The door is then secured for forces up to 4,200 pounds.

Four local schools have installed the BOLO stick in their classrooms, including the Trumbull Career and Technical Center (TCTC).

TCTC Superintendent, Jason Gray, said, "We're always trying to upgrade our security, to add another level of safety for the students and I was looking for a safe affordable way to add that extra layer and the BOLO stick delivered."

One big concern, in an active shooter situation, is the intruder can just break a window and reach in and open the door. The BOLO stick prevents that.

At $80 each, the cost to reinforce all the doors at TCTC was around $4,000, a price officials said is worth the investment for student safety.

The inventor hopes schools around the nation will soon feel the same way.