‘Tragedy prevented’: Parent’s tip halts PA school shooting plot as police seize five AR-15 rifles
(Upper Yoder Police Department)

A parent's tip about a trespassing incident may have prevented a carefully planned and potentially large-scale school shooting in Pennsylvania this week.

Police say five AR-15-style firearms were seized from the home of one of the two suspects, 16-year-old Preston Hinebaugh, a student at Westmont Hilltop Junior-Senior High School in Johnstown.

The other suspect, 17-year-old Logan Pringle, is a former student who had been expelled for previously threatening "to shoot up the school," WJAC-TV reports.

On Tuesday, Hinebaugh reportedly let Pringle — who was not allowed on the property — into the school by opening locked doors. Surveillance video shows the pair wandering the halls and observing security camera locations.

"Hinebaugh allegedly posted a picture of Pringle inside the building with what (Police Chief Donald) Hess described as a 'kind of ominous-like' message about his return," according to the Tribune-Democrat.

After “an alarmed parent” alerted the school to the security breach, police searched Hinebaugh's home and found the weapons. The AR-15s reportedly were “ghost guns,” meaning they were untraceable firearms without serial numbers.

“Those guns were made and put together by somebody in the Hinebaugh family,” Chief Hess said.

The two teens have been charged as adults with multiple felonies, including conspiracy to commit terrorism.

District Attorney Greg Neugebauer told WJAC, " I do believe tragedy was prevented."