Montoursville police take Yaa-sir Jennings-Cornelius to the Lycoming County Prison after he was arraigned on charges of threatening to "shoot up" Montoursville High School. PHILIP HOLMES/Sun-Gazette

A Williamsport teen who authorities say threatened to “shoot up” the Montoursville Area High School pleaded guilty to making terroristic threats and harassment before Lycoming County Judge Ryan Tira Friday morning.

Yaa-sir Nassi Jennings-Cornelius, 18, of 812 Third Ave., Williamsport, was arrested on the charges following an Oct. 2 phone call through the social media app, Snapchat, during which he made the threat, which was heard by several students, court documents said.

The incident was reported to a school resource officer, and the victim and the others who heard the threat were kept in a vice principal’s office until the end of the school day as a safety precaution.

Sentencing on the matter is scheduled for Sept. 2.

A related case will move to trial, as Jennings-Cornelius is also facing a receiving stolen property charge in relation to the weaponed referenced in the threat.

Eight days prior to the threatening phone call, a video of Jennings-Cornelius was posted on Snapchat showing him “pointing a silver-over-black handgun at the screen,” according to an affidavit filed by a detective assigned to the county’s Narcotics Enforcement Unit.

It was later learned that the gun was one of several firearms stolen in a burglary at the Blued Barrel Gun Shop on Railroad Street in Hughesville overnight Sept. 20, the court document stated.

Jennings-Cornelius told authorities that the gun was “provided to him by a known juvenile,” who has since been arrested by state police for his involvement in the burglary at the Hughesville gunshot.

When the juvenile was arrested on Sept. 25, he had in his possession the same firearm Jennings-Cornelius was allegedly seen holding in the Sept. 24 video, according to investigators.

No trial date has been set for the firearms charge.