A string of false school shooting threats is instilling fear in school districts across the United States as they grapple with recent mass shootings.

“Swatting,” the act of making hoax phone calls to emergency services, is steadily on the rise. At least ten states have reported an influx of swatting calls since late last year, and the effects are only amplified in the wake of mass shootings, such as at The Covenant School.

The state of New York was placed on high alert three days after the mass shooting at the Nashville elementary school. Dozens of schools across the state found themselves in lockdowns on March 30 due to receiving shooting threats.

While each of the threats were determined to be unfounded, parents in the Town of Onondaga told CNY Central that their hearts “dropped” when they learned of the incident.

Schools are treating each threat as legitimate amid the trend. In Rhode Island, where more than a dozen schools were targeted on March 28, officials say they have a responsibility to respond each time.

Can you imagine the one time that law enforcement does not respond to it and it’s an actual event that happens?” Derek Borek, a retired Rhode Island State Police captain, told WJAR.

That responsibility is taking a toll on local law enforcement in several states.

In Texas, police officers are being pulled from their standard assignments to respond to false threats. The unnecessary response equates to a loss of both time and resources for their respective departments.

Anyone who's available is gonna come to a situation like this,” Sgt. Washington Moscoso of the San Antonio Police Department told WOAI Friday. “Some people get a kick out of it, some people think it's funny, we take it very seriously.”

The effects are felt in the classroom as well. Experts believe that swatting calls, especially in the wake of mass shootings, can lead to post-traumatic stress disorder, depression and difficulty focusing for students.

One Rhode Island father told WJAR that his son struggled to “cope” for days after his school was targeted. In Pennsylvania, where schools across the state received computer-generated swatting calls two weeks ago, students say the threats are “disgusting and terrifying.”

Lawmakers are beginning to echo those sentiments, as Senate Majority Leader Chuck Schumer is demanding the FBI start stepping in.