Another student informed a resource officer at the school about the situation.
"Upon receiving this information, we immediately responded to verify the credibility of this allegation," said Sgt. Christopher Cook of the Arlington Police Department
The school was placed on lockdown just before 9:00 a.m. Tuesday and remained that way for more than three hours. Police searched the entire school room to room and brought in K-9 officers to search lockers and common areas.
According to school district spokeswoman Amy Casas, the lockdown situation effectively meant that nobody was permitted to enter or exit the campus.
Just before 12:30 p.m. a school district spokesperson confirmed the lockdown had been lifted and that no weapon had been found. Administrators said police in Arlington were also "confident that the suspect is not on campus."