"Marriott Islamabad ..." The YouTube account associated with this video has been terminated due to multiple third-party notifications of copyright infringement.
Sorry about that.
The hotel shortly after the explosion. 
CCTV footage has been released showing a truck bomb exploding outside the Marriott Hotel in Islamabad, Pakistan. The footage shows a camera, which was manually controlled to focus specifically on the developments as they happened.

The nearly four minutes of footage, shows a large truck pulling up in front of the hotel at a guarded gate. After the truck attempted to ram through the barrier, some reports stated that guards began to fire shots into the truck.

"The truck was stopped at the barrier and there was an altercation between the attacker and the guards," said Pakistani Interior Ministry official Rehman Malik in a statement to the press.

Guards began to run away once the truck slammed into the gates, but began to approach the truck seconds later. The cabin of the truck then explodes sending sparks and debris in all directions, with some of it hitting the camera. The truck begins to catch fire and people can be seen returning to the scene in an attempt to put out the blaze. Unsuccessful, the truck explodes, taking the camera out with it.

Officials believe al-Qaeda is responsible for the attack which killed 53 people and injured almost 300. Rescuers are searching for survivors, as an unknown number of people are still missing. At least 21 of those killed were from foreign countries.

Officials say the target was aimed for a residence a block away which was said to be housing Asif Ali Zardari, Pakistan's new prime minister. He was attending a dinner with several other Pakistani officials.