BUTLER TWP — A teenager is accused of threatening two girls with a knife last week at a skating rink where a school activity to promote positive peer pressure was being held.

The girls, 12 and 14, told authorities that Robert J. McCarl, 18, of Butler Township pulled the folding knife and threatened to cut them, according to court documents.

He allegedly placed the open blade against the younger child and ran it along down her back.

No one was injured but both girls were visibly shaken by the altercation about 8 p.m. Feb. 3 at the Skate Castle on New Castle Road, township police said.

Police on Monday charged McCarl with two counts of aggravated assault, a felony.

He also is charged with two counts each of terroristic threats, simple assault and harassment, and a lone count each of reckless endangerment and disorderly conduct.

Police said the girls were at the rink as part of the Stand Tall program, which encourages students to live a healthy drug-free lifestyle and steer clear of negative peer influences.

Neither child knew McCarl, who attended the activity with his younger brother and sister.

The alleged victims told investigators that McCarl approached them and made a veiled threat. The girls initially believed he was joking until they saw the knife, documents said.

A 13-year-old girl at the activity reported seeing McCarl put the knife back in his pocket.

The incident was reported to the school police officer, who confronted McCarl and took the knife.

McCarl’s father was called to pick up his children, and the school officer returned the knife to the father.

Police on Thursday interviewed McCarl at the station. He claimed the alleged victims flirted with him and he told them to leave him alone, according to court documents.

He said he later overheard the girls make what he apparently believed was a threat against his sister.