A convicted school shooter and two other Ohio inmates spent several months building a ladder that they used to escape from prison.

Ohio's prisons department released details on Friday that explain how the three managed to get onto a prison roof in September and jumped to freedom. All three were caught within hours of the escape.

The report says T.J. Lane and the two other inmates built the ladder with materials stored in a maintenance area at the Allen-Oakwood Correctional Institution in Lima.

The investigation also found that a security camera at the unit where the escape happened wasn't working and that some lighting near the prison needed to be repaired.

Lane is serving a life sentence for killing three students in 2012 inside a school near Cleveland.