The public execution was captured on video.
Masked gunmen, some wearing green armbands associated with the Palestinian militant group Hamas, lined up eight prisoners in the middle of a crowded street in Gaza city on Monday. They forced the men to bend over, pointed their rifles at them and opened fire, leaving their bodies in the dirt.
A Hamas internal security official confirmed that the video, which The New York Times geolocated to Gaza City, showed Hamas fighters executing Palestinian rivals in the Gaza Strip. He spoke on condition of anonymity because he was not authorized to speak to reporters.
The execution came just days after the start of a ceasefire with Israel on Friday and the withdrawal of Israeli forces in parts of Gaza. According to analysts, Hamas appears to want to assert that it is still the dominant force in the territory, no matter how weakened it is after two years of war with Israel.
Hamas has lost many of its top commanders and thousands of fighters in the conflict, and some Gaza residents launched rare protests against the group's iron fist earlier this year.
Israel has acknowledged that it has also tried to weaken Hamas's control by supporting rival Palestinian clans in Gaza, with mixed results.
“Hamas is sending a message: 'We are here. We are the only authority in Gaza,'” said Tamer Qarmout, a Palestinian political analyst and academic from Gaza, who lives in Qatar.
Since Monday, at least 10 members of Hamas security forces and at least 20 members of rival Palestinian groups have been killed in internecine clashes, according to a Gaza health official and a Hamas internal security official.
It is unclear whether the eight men executed in the video were included in the toll. They include members of the Doghmosh family, which has a long-standing rivalry with Hamas, Nizar Doghmosh, a leader of the family, told the Times on Wednesday.
The outbreak of domestic violence in Gaza, which has so far been limited to a few incidents, could further complicate President Trump's vision for a post-war Gaza. His plan to end the war calls for Hamas to lay down its weapons, allow an international force to stabilize the territory and effectively end its 20-year control – demands the group has so far rejected.
After a visit to Israel on Monday coinciding with Hamas' release of its remaining hostages in Gaza, a reporter asked Trump whether the group would reassert itself as a police force in Gaza and shoot rivals.
Trump has suggested that the United States is not opposed, at least for now.
“They were open about it and we gave them approval for a period of time,” he said.
On Tuesday, Trump addressed the issue again, saying that Hamas had “taken out a couple of very bad gangs” and adding: “It didn't bother me too much, to be honest.”
During the war, Hamas fighters in uniform were rarely seen on the streets of Gaza. They avoided moving outdoors as much as possible so as not to be targeted by Israeli air strikes.
Palestinian witnesses in Gaza say groups of masked Hamas security officers armed with rifles are reappearing, even as Hamas handed over the remaining hostages to the International Committee of the Red Cross on Monday.
Some of Hamas' activities appear to involve restoring public order to daily life.
In the central city of Deir al-Balah, armed men were spotted in the streets this week directing traffic, something that was unlikely to happen during two years of war.
Hamas officials publicly acknowledge that they are also launching operations against people they believe are transgressors or collaborators with Israel.
Two Hamas internal security officials said the killings shown in the video were in retaliation for the killing of several Hamas militants by the Doghmosh family during the war.
The clashes that led to the killings shown in the video began on Sunday, Doghmosh said, after family members shot and killed the son of a Hamas commander who accused them of being collaborators. Mr Doghmosh denied that the family was working with Israel.
Later that evening, Hamas fighters and armed members of the Doghmosh family fought a firefight in Gaza City, according to two Gaza health officials, two Hamas internal security officials and Palestinian residents.
One of the people killed in the clashes was Naim Naim, whose father, Basem Naim, is a senior Hamas leader, according to two family members and one of Gaza's health officials.
After the clashes, armed Hamas fighters raided nearby homes, checking identity cards to see who belonged to the Doghmosh family, said a Palestinian witness who asked not to be named for fear of retaliation. He said his family spent hours huddled in the center of their home amid a hail of gunfire and explosions outside.
Then Hamas fighters arrived and ordered them to flee, he said.
At least 24 bodies have arrived at Al-Shifa hospital in Gaza City following clashes between Hamas and Doghmosh on Sunday night, said Mohammad Abu Salmiya, director of the medical facility. He said he didn't know how many were on each side.
On Monday, the day after the Gaza City clashes, Hamas gunmen were filmed shooting at masked and blindfolded men in the middle of the neighborhood where the clashes took place, surrounded by a large crowd of passers-by.
Hamas' Interior Ministry has warned rival groups that it will persecute any “criminal gang” that threatens “civil peace”. Mahmoud Mardawi, a Hamas official, vowed on social media on Tuesday that the group would not allow “chaos to spread to beloved Gaza nor allow criminals to escape punishment.”
Military analysts say one of the main targets of Hamas' crackdown is likely to be the series of small Palestinian militias that have sprung up in Gaza in recent months, although it is unclear whether Hamas has already moved against them in force. No one has yet mounted a serious challenge to Hamas, analysts say.
Some of these smaller militias claim to have worked in coordination with Israel.
Israeli Prime Minister Benjamin Netanyahu confirmed in June that Israel was “using clans in Gaza” to fight Hamas on its behalf. Israeli officials later confirmed they had helped arm a plane operated by Yasser Abu Shabab in eastern Rafah.
According to humanitarian officials, Abu Shabab was known to have looted humanitarian aid from United Nations convoys early in the war. Subsequently, he established a militia in an Israeli-controlled area within Gaza, claiming that this area would be peaceful and free of Hamas. His militia has uploaded videos showing makeshift classrooms and silent tents, in an attempt to lure displaced Gazans to join.
“This adventure would only end one way,” said Michael Milshtein, a former senior Israeli intelligence officer. “We armed and supported these militias, and now Hamas is coming for its revenge.”
If Hamas attacked any of the Israeli-affiliated clans, it would pose a “heavy dilemma” for Israeli authorities, who would have to decide whether to defend them – thus breaking the ceasefire – or allow them to be killed or arrested, Milshtein said.
For now, many militias say they have no intention of surrendering to Hamas.
“We are preparing to defend ourselves by any means necessary if Hamas attacks,” said Mohammad al-Mansi, 21, whose father leads a small armed group opposed to Hamas in northern Gaza.
“We won't turn ourselves in. We'd rather die.”
Bilal Shbair AND Abu Bakr Bashir contributed to the reporting.