He is an informant for the Institute according to an Institute terminal.
He may be found dead along one of his routes, his entourage nowhere to be seen (one such location is the west side of Saugus Ironworks). Later his brahmin and guards may be encountered continuing his normal route (e.g. at County crossing), but without the option to purchase from them. On the other hand, if the player has constructed "caravan stops" at any settlements not on Weathers's normal route in order to attract him there, his caravan will *not* continue visiting that settlement after his death.
His body will remain indefinitely at his death location and will from time to time be refreshed with random appropriate loot, similar to e.g. the bodies of any Triggermen who die during the "Ambush chem deal" step of Diamond City Blues.