In the early morning of June 1, a large number of Palestinians were killed with claims it happened as they were trying to approach a new aid distribution centre near the southern Gazan city of Rafah.
The International Committee of the Red Cross said its field hospital received 179 casualty cases that morning, the majority with "gunshot or shrapnel wounds", with 21 declared dead on arrival.
The Hamas-run Gaza health ministry said 31 people were killed and accused Israel of turning aid centres into "death traps".
Israel's military rejected claims it was responsible, calling the allegations "false reports".
The organisation which runs the aid site, Gaza Humanitarian Foundation (GHF), said its activities on Sunday passed "without incident", dismissing "false reporting about deaths, mass injuries and chaos".
UN chief António Guterres is now calling for an "immediate and independent investigation".
Israel does not let international news organisations into Gaza, making confirming exactly what happened more difficult.
ABC NEWS Verify has analysed statements, security footage, satellite imagery, and videos from the ground, to try and paint a clearer picture.
The path to the aid centre
At the centre of this incident is the Tel al-Sultan aid distribution centre, near Rafah, which is run by the new US-Israeli-backed GHF.
This satellite image was taken more than a week ago, but ABC NEWS Verify has seen more recent imagery which shows the layout has slightly changed.
The GHF's official Facebook page gives clues into the timing of events that morning.
On May 31, at 8:35pm, local time, the GHF posted: "Severe danger. Please do not go or remain on roads leading to the distribution site at night — there is military activity."
On June 1, at 3:26am, it posted: "Please do not go to the distribution centers until we officially inform you that the centers are ready."
Shortly after, at 4am, it posted a document that said the aid point at Tel al-Sultan would be the only aid point working that day, and residents from one neighbourhood could access the site from 5am.
It featured a map showing Gazans where to walk for "safe passage".
"The safe passage to Tel Sultan will be via Al Rashid Street. The IDF will be present in the area to secure the passage. Use of the passage is prohibited before 5:00am, as the IDF has informed us that it will be active in the area before and after the specified safe hours."
At 5:10am, another post: "Tel Sultan site is now closed."
On the next day's document, the warning had the following added line, and a large "STOP" sign had been placed on the route on the map.
"In coordination with the IDF, for your safety, movement on Al Rashid Street after the Al-Alam roundabout is prohibited until 5:00 am."
By 5:24am, the aid site had closed.
The incident location
Witness testimony from people who were there helps to narrow down the location where the incident may have taken place.
On the approved route to the aid centre, on Al Rashid Street, there is a roundabout — sometimes referred to as Al-Alam. A source in Gaza told the ABC there is also a new mosque nearby.
This location has been referenced a number of times in reporting on the incident.
Ikram Nasser to ABC NEWS:
"By the time we arrived, there were gunfire and shots, so we hid behind the wall of Muawiyah Mosque."
Abdulrahman Odeh to the New York Times:
"At approximately 4:30am, before he had reached the distribution point, the shooting started."
A journalist in Rafah to BBC News:
"A crowd of Palestinians had gathered near al-Alam roundabout in Rafah, close to the GHF's site … when Israeli tanks approached and opened fire."
Eyewitnesses to CNN:
"Multiple eyewitnesses told CNN they were fired upon at what is known as the 'Al-Alam' roundabout approximately 800 meters from the site run by the GHF in southern Gaza."
One video posted on social media on Sunday showed people lying in the sand taking cover as shots rang out.
There aren't enough features visible to confirm its exact location — ABC NEWS Verify spoke to the teenager who filmed it, and he confirmed it was filmed at 5am, local time, on Al Rashid Street, on the way to the aid centre, though, he couldn't say exactly where.
A separate graphic video, which couldn't be verified due to its lack of features, claims to show people dead on the ground on a flatter section of road. The ocean is visible at times on the right of the scene, as it would appear if heading towards the aid centre via Al Rashid Street.
The GHF said it can't know what happened outside its centre.
"We don't control the area outside of our distribution sites and surrounding vicinity and we have no knowledge regarding IDF activities beyond our perimeter, which is still an active war zone," it said in a statement.
The IDF rejected allegations it was involved in the incident.
"False reports have been spread, including serious allegations against the IDF regarding fire toward Gazan residents in the area of the humanitarian aid distribution site in the Gaza Strip," it said in a statement.
"Findings from an initial inquiry indicate that the IDF did not fire at civilians while they were near or within the humanitarian aid distribution site and that reports to this effect are false."
But an Israeli defence source has told the ABC that approximately one kilometre away from the aid distribution site, outside of its operating hours, IDF soldiers "acted to prevent several suspects from approaching the troops", with warning shots fired towards those people.
The source insisted there was no connection between this and the incident in question.
The GHF maintains "nothing happened at or in the vicinity of our site".
Aid footage released
Security camera footage released by the GHF — which contained no time-stamps, metadata, or audio — appears to show what's known as tracer rounds being shot into the air as the aid station is opened.
Tracer rounds are bullets that contain a chemical that ignites when fired to make its trajectory visible. It is often interspersed among regular rounds.
Analysing the footage, ABC NEWS Verify can show the camera's approximate field of view — with the red lines representing the edge of the frame, and the purple dots showing light poles.
Twice in the CCTV footage — at 2:29 and 3:10 minutes into the video — red streaks can be seen flying into the sky, in the first instance from a point off camera, and in the second, from a location in front of the trees, between the third and fourth light pole from the camera.
ABC NEWS Verify showed a clip of the footage to two weapons experts, with both agreeing it showed tracer rounds shooting into the air.
"They're tracers but not following the same path, which means they're coming from two separate firing points (in the second instance)," said Mikey Kay, a former senior British military officer, and host of The Security Brief on BBC News.
"The speed tells me it's quite high calibre weapons."
Identifying the exact weapons used is difficult, especially without sound, but a man in the centre of the frame begins running, after previously walking, after the second tracers are seen.
The appearance of tracer rounds implies, at a time when the aid centre was open there was shooting in the area from an unknown source.
The GHF initially told ABC NEWS Verify that the red streaks were "flares". It stopped responding to emails when asked if they were actually tracer rounds.
The IDF said: "Hamas does everything in its power to undermine food distribution efforts in the Gaza Strip."
In a separate incident, on Tuesday morning local time, about half a kilometre away from the aid site, the IDF said it fired shots at "individual suspects who were advancing towards the forces".
"Casualties are being reported, details of the incident are under investigation," it said in a statement.
At least 27 Palestinians were killed and dozens wounded, according to local health authorities.
IDF releases video
At 7:54pm, local time, on June 1, as details of the incident in Rafah were being reported, the Israel Defense Forces (IDF) released a message and video on its official Telegram channel.
It read: "Drone footage reveals: Armed men in Gaza shoot at Gazan civilians on their way to collect humanitarian aid."
The IDF claimed the video showed "armed and masked men throwing stones" at people trying to collect aid, in southern Khan Younis.
ABC NEWS Verify matched the start of the IDF drone vision, to an on-the-ground video posted at 3:22pm local time on June 1, from a Khan Younis neighbourhood Facebook page.
"Near Al-Tahlia in Khan Yunis [they] stole flour trucks, then started selling it by organising lines of citizens who came to buy," the post said.
"Using violence and intimidating them with batons and some light weapons under the pretext of arranging the queues."
The videos were matched using a post, trees, and a building which appeared in both videos.
ABC NEWS Verify contacted a resident in Khan Younis, who said the events in the video happened in the Al-Wafiye neighbourhood.
The suburb is almost 8 kilometres away from Rafah.
The IDF video was released on Telegram with the caption implying who was responsible.
"Hamas is a murderous and brutal terrorist organization that is starving the residents of Gaza," the caption read.
At least one figure in the video appears to be holding a rifle. And what looks like a shot is fired into the ground at one point. A second figure appears to be throwing dirt at another.
These moments in the video are cropped, so it is not clear if they happened at the same location and time as the other drone footage in the video.
The footage isn't high quality enough to tell if the figures are wearing Hamas uniforms.
