Three juvenile robbery suspects were taken into custody inside Fort Worth's Polytechnic High School Tuesday morning, school officials say.
The trio allegedly robbed a person nearby before running inside the school.
Fort Worth police said two of the juveniles were arrested, while the other one was detained, identified and released.
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One of the suspects was charged with aggravated robbery and bringing a weapon into a weapons-free school zone. The other suspect was charged with aggravated robbery.
Officials have confirmed the suspects were all students at Poly High School.
The school was locked down for about an hour. Teachers locked classrooms, turned off lights and some barricaded the doors.
"We were scared," said student Marisol Martinez. "I cried a little."
Police conducted a final sweep of the campus and the lockdown was lifted.
Under new security procedures, the doors to Fort Worth high schools are supposed to be locked during the day. It's still unclear how the suspects got in, but because they were students at the school they may have been allowed in by someone who didn't know what had just happened.
"I think the best thing to remember is that what we practice on a regular basis did work," said Fort Worth ISD spokesman Clint Bond. "No students, no staff was ever directly threatened by anyone and everyone is safe."
There were no injuries reported in connection with either the robbery or the incident on campus.
Polytechnic High School is located at 1200 Connor Avenue, southeast of downtown.
NBC 5's Holley Ford contributed to this report.