Hasan employed an FN 5.7 pistol.

The weapon is produced by arms manufacturer FN at Herstal in Belgium. Hasan was able to purchase the arm without any difficulty at an arms dealer's.

The 5.7 pistol is an extremely powerful semi-automatic weapon. Using a special type of ammunition, it can pierce through bullet proof vests even at a great distance.

This makes the weapon extremely popular among criminal gangs. It has been dubbed the "cop killer".

The US anti-guns lobby has been pressing for restrictions on the free sale of the arm but the authorities decided only to limit the sale of the ammunition.

Texas police sources say that Hasan was able to purchase the arm in a weapons' shop near Fort Hood.

Hasan had two weapons when he went on the rampage. He did not use the Smith & Weston pistol he also had with him.

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