By Robbie Owens

DESOTO (CBSDFW.COM) – In DeSoto, there were no signs Tuesday of the disruption that had the high school on lockdown Monday for hours.

“Our biology teacher had us go in a storage closet and we were told to stay there and be quiet,” says Sophomore student Tajhay Mackey, “and he shoved desks against the door.”

As is so often the case, the threat that was posted online was a hoax. And the community is frustrated that someone, somewhere has forgotten so quickly that school shootings are real. So online threats can’t be ignored.

“You have to take them all seriously,” says Gwendolyn Ballard in DeSoto. “Parents need to watch what their kids are doing online.”

A company called watchcenters.com, based in the Washington, D.C. area, discovered the threatening tweets. The firm searches the dark web for threats to government agencies, and stumbled upon tweets showing a man holding a weapon threatening to shoot up DeSoto High.

“It’s frustrating to see hoaxes such as the one yesterday,” says founder Bob Dowling, “but, the authorities and my team– we have no other option than to assume that it is serious and to assume that it’s real.”

Although the firm later determined that the picture attached to the tweet had been circulating online for years, staffers confirmed that the threatening tweet in fact originated in the DeSoto area. So in spite of the unnecessary alarm, Dowling says he has no regrets.

“We’ve been credited with stopping 20 planned public school shootings just by legally monitoring the internet and making appropriate, and real time notification.

(© Copyright 2018 CBS Broadcasting Inc. All Rights Reserved. The Associated Press contributed to this report.)