The Waterford School District has a police presence at both Durant and Mott high schools after a threat was made on Facebook by two teen boys.
The posting pictured a male holding a rifle with a caption that warned not to go to either school on Monday.
Police said they identified the person holding the gun, and a friend.
They determined the threat was a hoax.
Police said they were able to locate the gun and take it into evidence. It is a pellet gun.
Police said the case is being reviewed for possible criminal prosecution.