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ST. ANN, Mo. – St. Ann detectives are investigating a threat at Ritenour High School. The police arrested a 17-year-old student after he made threats on social media to bring a gun to school.

“It’s a scary thing when they send you messages at home throughout the day that there has been a threat made at your children’s school,” said Tammy Groceman.

She received a message Friday morning about a threat made at her daughter’s high school.

“A student had called in and said he wasn’t coming to school today because he was afraid,” said Lt. Colonel Charles Thal. “He was afraid because there was a post on Instagram. Two posts on Instagram that the school was going to get shot up today.”

He said the school resource officer and responding St. Ann officers immediately secured the school. Thal said the student who made the threat wasn’t in class Friday.

“They went to his home and arrested him,” he said. “And in the course of the arrest, they had a search and they recovered a small caliber handgun.”

Groceman said she is thankful the threat didn’t turn into something more.

“They moved on it fast, I will say that. They got right on it,” she said. “They got it all cleared up and took care of. So, that was good and they said they had extra officers up at the school today.”