Manfred was a well informed merchant passing through on the roads between Novigrad and Oxenfurt in 1272. At one point he stopped and camped out with two others: a Redanian soldier named Rufus and a sorcerer named Theophile Maria Rosco.
If Geralt stops by to talk and refuses to get involved or helps Rufus: Rufus killed Manfred, believing he was a spy, though he had no proof. On searching Manfred's body, he felt the Nilfgaardian florens the merchant had been carrying were enough to justify his suspicions.
If Geralt stops by to talk but then defends Manfred: Sadly, Geralt had no other choice but to kill Rufus, who was dead set on killing Manfred, believing he was a spy.
If Geralt stops by but leaves after introduction: Rufus and Mandred remained passive, and the original three men continued to camp out.