There were two novels that fulfilled this plot. They were Top-grade Medical Martial Expert and Top-grade Demonic Berserker. Among them, Li Yang, the main character of "Top Grade Medical Warrior", became a neighborhood security guard after he came out of prison, while the main character of "Top Grade Evil Soldier" became a part-time security guard of Yingying Campus after he came out of the prison of death. I hope you like my recommendation. Muah ~