What is in the tuple payload for VehicleSpawnedEvent?

I’ve modified my code per your suggestion, thank you.
this line of code is not successful:

PlayerVehicle = FortCharacter.GetVehicle[]

Full code:

    PlayerVehicle : ?fort_vehicle = false

    OnBegin<override>()<suspends>:void=
        # vehicle spawner
        ATK_Vehicle.AgentEntersVehicleEvent.Subscribe(OnAgentEntersVehicle)

    OnAgentEntersVehicle(Agent : agent):void=
        if:
            FortCharacter := Agent.GetFortCharacter[]
        then:
            Print("got FortCharacter")
            if: 
                PlayerVehicle = FortCharacter.GetVehicle[]
            then:
                Print("got PlayerVehicle")