Update: Dwight Satterfield with Decatur City Schools says Decatur Middle School and Oak Park Elementary were also on secure perimeter. He says they were on secure perimeter for 15 minutes.
Satterfield says the suspect who was trespassed did have a knife on him.
Decatur High School was placed on a secure perimeter on Tuesday after a man was reported to have a gun on the baseball field.
The secure perimeter has been lifted, and Decatur police say it was discovered the 20-year-old man had an airsoft gun.
The man was not arrested but was removed from the property for trespassing.