AUSTIN (KXAN) — An off-campus robbery involving students sent a northwest Austin high school into “secure” mode Monday, the Austin Independent School District said.

A letter to parents from Anderson High School Academy Director Drew Nichols said “police activity across the street involving Anderson students,” caused the response. In secure mode, all inside activity goes on as normal, but no one can go in or out of school buildings.

The Austin Police Department said the robbery happened in the 4400 block of Spicewood Springs Road, south of the high school. APD said there were two suspects, both minors, and one is in custody.

APD said witnesses confirmed both suspects are students at Anderson High School. APD received the call at 9:06 a.m.