What footage from the Moscow attack tells us about how it was carried out
On Friday evening, a group of gunmen carried out an attack at Crocus City Hall in Krasnogorsk.
The venue, located northwest of central Moscow, was partially filled with people in advance of a sold-out concert.
By Saturday night, at least 133 are reported to have been killed.
Video filmed over the course of the attack helps paint a picture of how it was carried out.
Sky News has determined that the perpetrators likely entered the complex around 130m north of the concert hall's foyer.
Footage filmed in this location shows bodies and a set of glass exterior doors that have been shot through. At least eight people appear to have been killed in this area.
A second video, filmed from an upper walkway shows the attackers moving towards the entrance of the venue's foyer. A group of people can be seen attempting to take cover to their left.
The gunmen stop to fire upon them at close range. They then break a set of glass doors and proceed through into the foyer.
Footage filmed soon after this shows the gunmen moving south through the foyer. One of the attackers can be seen reloading his weapon as he moves.
Videos filmed in the concert hall itself show large numbers of people attempting to flee the through its stage and rear exits.
Footage that appears to have been filmed soon after shows four gunmen shooting at the crowd from a seating area just below the first-floor balcony.
While the footage is not of suitable quality to accurately distinguish between dead, wounded, and otherwise immobilised people in all cases, many appear to have been killed in the auditorium.
As three of the gunmen continue to fire their weapons, one can be seen moving to the south of the room. He goes off camera, at which point something ignites close by.
Fire can briefly be seen at the nearby exit.
Eyewitness testimony translated by Sky News provides an additional perspective.
Recounting the event in a video uploaded to Instagram, a survivor said: "They broke into the hall - I don't know who it was, terrorists, military, whoever it was in brown clothes - and started shooting at people with automatic rifles.
"It was set on fire... There's smoke, there's smoke going all the way up into the sky."
The videos reviewed by Sky News suggests four gunmen carried out this attack. This matches the number provided by Russian authorities, who have stated that six additional people have been arrested in connection to the event.
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Videos from 23 March show the scale of the damage caused to the building the night before.
In one, shared by Russian authorities, emergency workers can be seen moving into the auditorium to the position from which the attackers fired upon the crowd.
The entire area is heavily fire-damaged, and large sections of the venue's roof have caved in.
Since the attack, the Russian government has alleged that the perpetrators intended to flee to Ukraine.
Addressing his nation, Vladimir Putin accused the Ukrainian government of complicity, claiming "a window was prepared for them on the Ukrainian side to cross the border".
These allegations have not been proven.
While all the suspects were reportedly apprehended in the southeastern region of Bryansk, no evidence has surfaced that reliably indicates their intended destination.
Since their arrests, footage has emerged that appears to show one of the suspected gunmen being tortured by Russian authorities.
A man can be seen being held down by Route E101 in Bryansk Oblast.
A later video shows the same man being led to the main road, with wounds visible on the side of his head. Sky News has verified the location of this video.