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At least twenty people were injured, some seriously, at the Franklin Regional High School outside Pittsburgh on Wednesday morning after "a person ran through the school slashing or puncturing students with a knife or other sharp object."

Officials have indicated that all those injured, despite the horrific nature of the attacks, are all expected to survive their injuries.

According to local NBC affiliate WPXI:

Westmoreland County emergency management spokesman Dan Stevens said one person is in custody.

Channel 11's Joe Holden reported that 20 people were hurt in the stabbings. At least four of the victims were seriously hurt.

The Associated Press adds:

Dan Stevens, the spokesman for Westmoreland County emergency management, said five or six people were reported stabbed at about 7:20 a.m. at Franklin Regional High School in Murrysville, about 15 miles east of Pittsburgh.

It wasn't immediately clear if the suspect and the victims are students, adults or a mix of both. It doesn't appear that any of the victims suffered life-threatening injuries, Stevens said, though several helicopters were seen flying people from the scene to area hospitals.

School officials and Murrysville police didn't immediately return calls seeking further details, but the school issued a bulletin on its website saying: "A critical incident has occurred at the high school. All elementary schools are canceled, the middle school and high school students are secure."

The district serves about 3,600 students who live in the bedroom communities of Murrysville, Export and Delmont. The elementary and middle schools are part of the same campus.

The high school was on lockdown, and students were being kept there as a precaution as school and law enforcement officials double-checked the premises. School officials were making arrangements to bus the middle school students home.

District Attorney John Peck said he was monitoring the situation. Detectives from his office were also investigating, though Peck said he had no information beyond that being reported by Pittsburgh television news stations.

The school is located in the town of Murrysville in Westmoreland County, approximately twenty miles east of Pittsburgh.

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