Palestinians take part in a protest to condemn what Gaza’s interior ministry said was the killing of a mentally-ill Palestinian by Egyptian forces, after he waded across the sea into Egyptian territory, in Gaza City December 27, 2015.

Palestinians in Gaza and on social media have expressed outrage over the death of a naked man who was shot as he crossed from the Gaza Strip into Egypt.

A video has spread online purporting to show the man walking in the Mediterranean surf and crossing the posts and fencing marking the border between the Palestinian enclave and Egypt.

Egyptian guards open fire, while someone who appears to be part of the Gazan security forces appears to wave and signal to those shooting to stop because the man is mentally unstable.

Officials from Hamas, the Islamist movement that rules the Gaza Strip, say he suffered from mental illness, though the father of the Gazan man has been quoted as saying he did not.

The video, taken on Thursday, later shows the man’s body on the shore. The Egyptian army has so far not commented on the incident.

The hashtag “Why did they kill him?” has since spread on social media and several dozen Gazans demonstrated on Sunday to demand Egypt return the man’s body to his family.

Gaza has been under an Israeli blockade since 2006, while its sole crossing with Egypt has been largely closed since the summer of 2013, when Egyptian president Mohamed Morsi of the Muslim Brotherhood was overthrown.

Cairo accuses Hamas, which is allied with the Muslim Brotherhood, of supporting attacks in Egypt.

The blockade and the closed Egyptian border means 1.8 million Gazans are effectively trapped inside the small enclave hit by three wars with Israel since 2008.

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