In an unexpected move Mansfield Spanish Immersion School principal Gabe Costa turned in his resignation to the Mansfield City School District at the end of last week. District spokesman Larry Gibbs tells riclandsouce.com he doesn't know why Costa resigned and there is a plan for an administrator to be in the school building this morning. Costa took over as principal of Mansfield Spanish Immersion in June of 2015 after teaching third grade in the building. Gibbs said he expected an interim-principal to be established sometime this week.