PARKLAND (CBSMiami/AP) – One of three Marjory Stoneman Douglas High School assistant principals reassigned after the 2018 mass shooting has been cleared by a school district investigation.

Winfred Porter Jr. and two colleagues at the Parkland school were reassigned a year ago after the superintendent promised disciplinary action tied to the district’s perceived failure to penalize anyone but a few low-level employees.

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Head of the investigative unit Craig Kowalski wrote in a letter to Porter that they found “an insufficient factual or legal basis exists” to establish just cause disciplinary action.

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Director of the Broward Principals and Assistants Association Lisa Maxwell says Porter was accused of problems that fell outside his job duties.

The letter says Porter is free to return to the school or remain in his current assignment.

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(© Copyright 2019 CBS Broadcasting Inc. All Rights Reserved. The Associated Press contributed to this report.)