A Syrian rebel group claimed responsibility for the Damascus bombing that killed four of President Bashar Al-Assad’s top aides, releasing video purporting to show the building minutes after the blast and radio messages from panicky security forces.

The video, circulated by the “Military Leadership of Damascus City and Province” in the name of the “Hawks Special Operations Battalion” showed drifting smoke near the National Security Bureau building in the Damascus district of Abu-Rummaneh which was struck, though no sign of outward damage.

Rebels using the name of other groups have already claimed to have carried out the July 18 attack. But the video, downloaded onto the Internet Saturday, was the first to show the apparent aftermath of the brazen blow against Assad’s inner circle.

Regional security experts who saw the video said it was apparent the camera had been fixed on the street where the National Security Bureau is located, near the now abandoned US ambassador’s residence, well before the explosion.

“Whoever took the video knew something was about to happen there, although they did not film the exact explosion, which appears to have killed its targets at close quarters from inside the building,” one of the sources said.

The eight-minute video showed a steady and clear shot of the building, unlike much of the footage distributed by Syria’s opposition, suggesting that the camera could have been set up in advance, although it did not show the moment of the blast.

It included recordings of apparently intercepted radio messages between anxious security forces calling for ambulances to be sent to the location in the aftermath of the attack.