YEADON, Pa. (CBS) — Yeadon police announced Monday that two teenage girls have been arrested in connection to an online threat against Penn Wood High School and Middle School. The threat was posted on Instagram, warning that someone was going to “shoot-up” the schools.

Yeadon Police Chief Anthony Paparo wants parents and students to listen up. He says all threats have to be taken seriously and will be prosecuted.

“I’m going to find you. I’m going to lock you up,” Paparo said.

He did not mince words when announcing two 13-year-old girls are now charged with making terroristic threats.

“Know that you’re going to get caught. You’re going to get found,” he said.

The 20-hour investigation began Thursday after officers say the two teens used Instagram to say a mass shooting was expected at Penn Wood 9th Grade Academy in Yeadon and Penn Wood High School in Lansdowne.

Eyewitness News was at both schools Friday, finding an increased police presence.

Paparo messaged the Instagram accounts himself and later connected the posts to the two girls.

“What makes it even more sickening is the parent kept the kid home Friday because of the threat,” Paparo said.

“One was a juvenile that lived in Yeadon, another was a juvenile that lived in Darby and the sad part is they were only 13 years old,” Yeadon Mayor Rohan Hepkins said.

No incidents ever happened but authorities hope this case sends a message about making threats.

“We’re 20 years past Columbine, we now know that we can never take any threat to the school community anything but seriously,” Delaware County District Attorney Jack Stollsteimer said.

Police say the two girls will likely not go to jail but probably get mental help.