A student from Perry Hall High School outside Baltimore is in custody after a shooting today, the first day of school, of another student, WUSA television reports.

The injured student was flown to a shock trauma unit, and the student’s condition is unknown. There are unconfirmed reports that the student was shot in the back, WUSA reports.

Parents indicate that the incident may have stemmed from a threat on Facebook reading: “First Day of School, Last Day of Life.” According to WUSA, bullying may have been involved:

“Maryland Gov. Martin O’Malley issued the following statement related to the shooting, WUSA reports:

“’Today, on this first day of school for many students in our state, we’ve suffered a senseless act of violence. I’d like to thank the teachers and administrators for their courageous and life-saving actions. At this time, our thoughts and prayers are with the injured student and his family.’”

Students Areille Brown and Miranda Wienecke told the Baltimore Sun that the shooter was stopped by staff members who intervened and stopped him by tackling him, embracing him with a bear hug and pinning him against a vending machine, USA Today reports.

As of 12:46 p.m. ET today,  there have been unconfirmed reports that the student taken to the hospital is a 17-year-old male, and the student in custody is a 15-year-old male.

Brown also told the Sun that students were in the cafeteria for about 15 minutes when they heard a popping sound reminiscent of the opening of a bag of potato chips.

Weinecke told reporters that she saw people running and getting under tables. Other students report being herded into classrooms by teachers.