BOONE COUNTY, Mo. -

After a deadly Oregon high school shooting Monday, the community grieves and asks the question: Why?

The question so many have about school shootings over the last months.

ABC 17 News asked local law enforcement if there are certain behaviors they watch for in students.

"We've had violence in schools even back to the early 1800s," said Sergeant Brian Leer with the Boone County Sheriff's Department, who oversees the school resource officers. "You can find school violence situations and it ranges from students to adults, and people not even associated with schools occasionally. It kind of goes hand in hand with the violence in the rest of society."

"When you try to come up with a set profile for a shooter, it's kind of like coming up with a set profile for a shooter in the United States, because they all happen for different reasons," Leer said.

Which is what he said makes it a challenge to understand what drives a shooter in these situations.

But law enforcement is trained to keep an eye on certain things.

"Any indication that somebody may be considering doing something violent at the school, as far as our schools, I can speak for the ones we work in, we take these things very seriously," Leer said.

Statistics do show some similarities in active shooter situations in schools, the first being that the shooters are generally male and act alone.

"The other common characteristic that we see when we look at statistics on school shootings around the country is the perpetrator tends to have some type of grudge that they're following up on," Leer said.

But he said there are instances where that isn't the case.

Leer said every report of a potential threat of violence is followed up by school resource officers in Boone County. The officers attend conferences each year that teach them certain types of behavior to keep an eye on.