If you can cause damage via the fort_character in verse, the API lets you provide a damage instigator, so you can pass the other player as the instigator.
if:
Char := Agent.GetFortCharacter[]
Instigator := game_action_instigator[Char]
then:
Args : damage_args = damage_args{Instigator:=option{Instigator},Amount:=200.0}
Char.Damage(Args)