Twenty people were wounded Wednesday morning in a stabbing rampage at a high school in Western Pennsylvania, officials said. Four students were reported in critical condition.

A 16-year-old student was in custody following the attack at Franklin Regional High School in Murrysville, Westmoreland County, 15 miles east of Pittsburgh.

The victims included 19 students and a security guard, officials said,

Dan Stevens, Westmoreland County’s deputy emergency management coordinator, said the student victims included range in age from 14 to 17. Four were airlifted to area hospitals in serious condition.