Some 4,500 Palestinian security prisoners in Israeli jails went on hunger strike Sunday to protest the death of Arafat Shalish Shahin Jaradat in Megiddo Prison on Saturday.

Prisoners refused breakfast and lunch, and were expected to continue the “strike” for another one or two days, officials said on Sunday afternoon. Sources noted that the prisoners’ refusing meals was not exactly the same as a genuine hunger strike, in that they have access to other food outside of official prison meals.

Jaradat died of an apparent heart attack Saturday afternoon, according to Prison Services spokeswoman Sivan Weizman.

Following the announcement of Jaradat’s death, prisoners briefly rioted in the Ofer Prison in the West Bank. In Hebron, Palestinian protesters clashed with security forces, who dispersed them using tear gas. No injuries were reported.

Palestinian Authority Prime Minister Salam Fayyad said he was “Shocked” at Jaradat’s death. A statement issued by his office called on the Israeli authorities to find out the “true cause” of his death as soon as possible.

Israel’s domestic intelligence agency, the Shin Bet, said in a statement to reporters that the 30-year-old Jaradat was arrested on Feb. 18 after residents in his West Bank village of Saeer said he was involved in a rock-throwing attack that injured an Israeli citizen. Jaradat admitted to the charge, as well to another West Bank rock-throwing incident last year, the Shin Bet said.

Jaradat suffered from back pain and had been injured in the past by a rubber bullet and tear gas canister, the Shin Bet said. But he was examined a few times by a doctor who detected no health problems, and his interrogation continued, the agency said.

Jaradat’s uncle Musa told the Palestinian Ma’an news agency on Saturday evening that his nephew had been in “excellent” condition at the time of his arrest. He said the 30-year-old had been held at a detention facility for four days before being transferred to Megiddo.

The deceased’s wife, Dallal, said her husband left two small children. She said that though her husband had been arrested in the past, this was the first time he had been told by the arresting officer to bid his children farewell.

“This time, that officer sounded strange,” Dallal was quoted as saying. “That’s why I was very worried.”

Jaradat fell ill after lunch on Sunday, and medics were unable to resuscitate him. A Shin Bet spokesman, speaking on condition of anonymity in line with protocol, said Jaradat was not beaten during his interrogation, nor did he undertake any physical activities that might have led to a worsening of his health.

Weizman said Jaradat, who was arrested last week, had not been on hunger strike.

Still, his death is likely to enrage Palestinians at a time when they have been stepping up demonstrations in protest of Israeli-held Palestinian prisoners, especially four long-time hunger-strikers, including one whose health is rapidly deteriorating.

Demonstrators are principally demanding the release of hunger-striking prisoners Samer Issawi, Ayman Sharawneh, Tareq Qaadan, and Jafar Azzidine. Issawi has been on hunger strike for over 200 days.

Issawi and Sharawneh were previously jailed for long prison sentences for terrorist activities, but were released in 2011 as part of the prisoner exchange deal that secured the freedom of kidnapped Israeli soldier Gilad Shalit. Both men were since re-arrested for violating the terms of their release. Issawi — whose original convictions included attempted murder, for actions including opening fire on an Israel bus with an AK47 — was sentenced to eight months for the violation on Thursday.

Israeli police have opened an investigation into the prisoner’s death, the Shin Bet statement said.

On Saturday night, Israeli media reported that defense establishment officials had invited the Palestinian Authority to take part in Jaradat’s post-mortem examination.