Humphrey of Hauteville, as count of Apulia, had married the sister of the Lombard prince Guaimar IV of Salerno in 1051.

Gisulf, the eldest son and successor of Guaimar and Gemma, daughter of the Capuan count Laidulf, had been made co-prince with his father in 1042 while very young.

Only a decade later, on June 3, 1052, his father is assassinated in the harbor of his capital by four brothers of his wife Gemma, sons of Pandulf V of Capua, who had been goaded into the act by the pro-imperial partisans of Amalfi.

Guaimar's brother Pandulf of Capaccio is also killed, but Guy of Sorrento escapes while Guaimar's sister and niece are locked up.

The brothers-in-law seize the city and elect Pandulf, eldest among them, prince.

Young Gisulf is taken captive by the assassins, but soon his uncle Guy garners a Norman army under Humphrey of Hauteville and besieges Salerno.

The assassins' families soon fall into their enemies' hands and they negotiate their release by releasing Gisulf to Guy.

Guy accepts their surrender soon after, promising not to harm them.

The Normans, however, who maintain they are not bound by Guy's oath, massacre the four brothers and thirty-six others, one for each stab wound found in Guaimar's body.

Thus the Normans show their loyalty to Guaimar even after his death.

The city soon surrenders and Guy and the Normans pay homage to Gisulf, who confirms their titles and lands.

The rocky start to his reign us merely an indication of its character, for Gisulf will hold a grudge against the Amalfitans who had initiated the slaying of his father.

He also, for reasons unknown, will also come to hate the Normans as barbarians and will spend his entire reign in opposition to them.