(Screenshot from YouTube)

The suspected attacker is a student at school and is currently in custody. He reportedly entered the school wielding a knife before the first class of the day began. 

The stabbing attack occurred at around 7:20 a.m. at Franklin Regional High School, about 20 miles east of Pittsburgh. 

The school website posted the following emergency message: "A critical incident has occurred at the high school. All elementary schools are cancelled, the middle school and high school students are secure. Additional information will be released as soon as possible. Please keep our campus clear of traffic."

This is a developing story. Check back for updates. 

Read more at CNN.

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