Friedrich is involved in the quest The Destruction of Lothering. If Hawke takes up employment with the Red Iron mercenaries, Meeran will assign Hawke a contract: kill Friedrich and his guards. Upon confronting Friedrich, he will plead for mercy. Hawke may accept a bribe from Friedrich. However, his guards deduce that Friedrich has given away their wages, and so attack Hawke after Friedrich flees.
Alternatively, Hawke can kill Friedrich.If Friedrich is killed, his family will hire the Antivan Crows to assassinate Hawke. This is revealed in the Mark of the Assassin (quest) in the Mark of the Assassin DLC if Hawke searches the body of the Crow leader.