Student in custody after gun detected at Hillgrove High School

COBB COUNTY, Ga. - Hillgrove High School was placed on lockdown Tuesday morning after a gun was detected on campus, according to a letter from the school to parents obtained by FOX 5.

What we know:

A parent of a student at the school sent the letter to FOX 5. It said the school was placed on "Code Red" status—the highest security level in Cobb County Schools—after a student reportedly had a gun.

A 15-year-old student was apprehended within 12 minutes of the report of a gun on campus, according to the school district. Nobody was injured.

The school later returned to "Code Green" status, which is normal operating status.

Dig deeper:

SKYFOX 5 flew over the school around 12:45 p.m. and saw a long line of what appeared to be parents standing outside the front entrance of the school. There were also groups of students spread throughout the campus.

What we don't know:

At this time, it is unclear how it was discovered the student had a gun or if the gun was pulled out. According to the Cobb County School District's website, all high schools in the district are equipped with weapons detection systems.