A fourth woman, 27-year-old Ghada Karouah, died of gunshot wounds later in the day.
Nour Odeh, Al Jazeera's Gaza correspondent, said the killing of the Hamas member is unlikely to signal a return to violence between Hamas and Fatah.
"This was a revenge attack for the killing of a Palestinian from a rival Gaza clan some months ago."
"This a tribal society and part of the Mecca agreement is the formation of national committee to resolve the recent killings by rival factions. This process hasn't got started yet."
Hamas statement
Earlier this month Fatah and Hamas agreed in Mecca, Saudi Arabia, to forge a Palestinian national unity government.
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Palestinians hope the coalition deal will end violence between Hamas and Fatah in which more than 90 people died.
The Hamas-led interim Palestinian government issued a statement denouncing the violence, calling it a violation of the Mecca agreement, the AFP news agency reported.
"The Palestinian government denounces the attempts by some to violate the Mecca agreement and return the region to the spiral of violence and bloodshed," the statement said.
Clan rivalries have grown increasingly common and deadly in the Gaza Strip since security and other public services broke down due to the deadlock between the two factions.