Peregrine Island bank robbery mission - defeating hero doesn't complete mission

[Uun]

Ran the PI bank robbery mission. Robbed the bank and defeated the hero and everyone else inside the bank. Still read "Defeat hero to escape". Ran around the map for 10 minutes defeating PPD and KoA and running side missions, went inside the police station and freed the prisoner. While I defeated multiple Longbow ambushes, the mission wouldn't complete and I ultimately failed the mission.