Career
Originally from Yibna, he began his involvement in the General Union of Palestinian Students. In 1968, Youssef was appointed to the Executive Committee of the Palestine Liberation Organization. Two months before his death, Youssef was interviewed by the Beirut newspaper L'Orient-Le Jour.
In it he explained his conviction to the Palestinian cause: "We plant the seeds, and the others will reap the harvest. Most probably we'll all die, killed because we are confronting a fierce enemy. But the youth will replace us."
Youssef was alleged to have been linked to the 1972 Munich massacre, in which 11 Israeli athletes and coaches were killed either while resisting their assailants, or in the crossfire between the German police and the Black September group.
This prompted Israel to launch a revenge campaign called Operation Wrath of God, with Youssef as a principal target. In 1973, Israel sent commandos to Beirut, Lebanon to kill a number of high level PLO officials in the 1973 Israeli raid on Lebanon. A Hospital in Rafah was named for him.