DALLAS (AP) — Police have arrested a 13-year-old girl who is accused of posting a threat to shoot up her Dallas middle school on Instagram.

Dallas Independent School District police say they believe the girl posted the photo of a man with a gun to attract more followers. Investigators say the photo caption warned that everybody at T.W. Browne Middle School was going to die and that eighth graders would be targeted at a specific time.

The teen told police that she found the photo online.

Police say the girl, whose name hasn't been released, faces a juvenile charge of making a terrorist threat. Conviction carries penalties of up to 10 years in prison.

School officials were informed of the photo Monday night. Patrols were increased Tuesday.