The district revealed the ownership of the weapon after a Clovis parent said his son found the gun inside a restroom stall at Veterans Memorial Stadium during the season-opening football game, where thousands of students, parents and community members were gathered.
According to the father, his son stayed outside the stall to prevent anyone from accessing the firearm while his friends went to notify officers.
Clovis Unified officials said the district's police department is working with the California Department of Justice regarding the incident.
Action News also contacted the California Department of Justice to ask whether the officer could face disciplinary action. In a statement issued late Monday, the department said:
"We hold our Special Agents to the highest standard and are committed to maintaining the utmost integrity throughout this process. We want to assure the community that we are actively investigating this incident and are committed to accountability and transparency."
The Department of Justice did not provide additional details. The investigation remains ongoing.