Rahbi Shalabi was killed on Monday amid rare clashes between local militants and the Palestinian security forces, who exercise limited authority in the Israeli-occupied territory.
The security forces had initially claimed Shalabi was beaten to death by "lawbreakers".
But on Thursday, the Palestinian Authority (PA) said in a statement that "after a diligent follow-up and reviewing all the details... the Palestinian National Authority bears full responsibility for his martyrdom".
The PA added that it was "committed to dealing with the repercussions" of the deadly incident "in a manner that ensures justice and respect for rights".
After the clashes that killed Shalabi and wounded a 16-year-old relative of his, Palestinian militant group Hamas condemned the security forces of the PA, which is dominated by its political rival Fatah party.
A video circulating on social media, which AFP was unable to independently verify, appeared to show Shalabi and his younger relative stopping their scooter near an armoured vehicle belonging to the Palestinian security forces before being shot.
The PA has partial administrative authority in the West Bank, which Israel has occupied since 1967.
Jenin and its adjacent refugee camp are a stronghold for armed factions who present themselves as a more effective resistance to the Israeli occupation, in contrast to the PA which coordinates security matters with Israel.
Tensions have been running high in the West Bank after the PA arrested several militants earlier this month.
On Thursday last week, armed men seized two official PA vehicles and paraded through the Jenin refugee camp waving flags of the Islamic Jihad group, which is allied with Hamas in the Gaza Strip.
There were then gunfights in the area which continued into Monday, despite efforts to calm the situation.
There was significant damage from the gun battles, with AFPTV footage showing smashed windows and fire damage at the local hospital on Saturday night.
The clashes between local militants and Palestinian forces have added to the already soaring violence in the West Bank, with Israeli military raids and settler attacks increasing since the start of the Gaza war in October 2023.
