Mr Zubeidi once was an almost untouchable figure in the gritty camp. Palestinian leaders envied the power he wielded over residents and Israeli soldiers feared his determination to fight them before he gave up armed struggle to manage the theatre.

But since May, Mr Zubeidi has languished in custody of the Fatah-led Palestinian Authority (PA), detained in connection with an attack on a Palestinian official. He has not been formally charged with a crime, which has infuriated his supporters who decry his detention as a miscarriage of justice.

When asked about Mr Zubeidi, Talal Dwekat, the governor of the Jenin governorate said: "The point of what we're doing is to try to deliver security, stability and rule of law to Jenin."

That effort began after the May 1 shooting attack on the residence of Qadoura Mousa, then governor of Jenin, who consequently died of a heart attack.

Palestinian security forces responded with a sweeping campaign of arrests in the camp and in surrounding villages. On May 13, they came for Mr Zubeidi.

Mr Dwekat declined to comment in detail on the investigation. But he said investigators discovered that a local commander of one of the PA's security agencies ordered the attack on Mousa's home and that by the time Mr Zubeidi was detained, the weapon was in his possession.

"We're trying to determine whether he knew the weapon had been used in the attack," said Mr Dwekat.

Mr Zubeidi's family and lawyer, for their part, do not dispute that he had been in possession of the firearm after the attack.

Although denying he knew it was used in the attack, their accounts differ about what Mr Zubeidi did after obtaining the weapon, described as an assault rifle.

His 38-year-old brother, Abed, said an accomplice in Mousa's attack hid the weapon at a building that the Zubeidi family had rented out to a 23-year-old camp resident.

Mr Zubeidi had the weapon for several days after agreeing to take it off the resident's hands because, Abed said, "he did not want this young guy to be in possession of such a dangerous weapon".

Abed added that after his brother was detained, Mr Zubeidi had agreed to hand the weapon over to the PA.

But Farid Hawwash, Mr Zubeidi's lawyer, said Zacharia had notified the PA of the weapon and agreed to deliver it to authorities but then security personnel, in a surprise move, detained him.