On 13 December 2001, five terrorists infiltrated the Parliament House in a car with Home Ministry and Parliament labels. While both the Rajya Sabha and Lok Sabha had been adjourned 40 minutes prior to the incident, many members of parliament (MPs) and government officials such as Home Minister LK Advani and Minister of State for Defence Harin Pathak were believed to have still been in the building at the time of the attack. More than 100 people, including major politicians were inside the parliament building at the time. The gunmen used a fake identity sticker on the car they drove and thus breached the security deployed around the parliamentary complex. The terrorists carried AK47 rifles, grenade launchers, pistols and grenades.
The gunmen drove their vehicle into the car of the Indian Vice-President Krishan Kant (who was in the building at the time), got out, and began shooting. The Vice-President's guards and security personnel shot back at the terrorists and then started closing the gates of the compound. A similar attack was carried out on assembly of Srinagar, Kashmir, during November 2001, when 38 people were killed by terrorists.
Delhi Police officials claimed that gunmen received instructions from Pakistan and the operation was carried out under the guidance of Pakistan's Inter-Services Intelligence (ISI) agency. In their book The Exile: The Flight of Osama bin Laden, Cathy Scott-Clark and Adrian Levy state that then-CIA station chief Robert Grenier and Ambassador Wendy Chamberlin suspected that the ISI had approved the attack in order to force the redeployment of troops under the command of Ali Jan Aurakzai away from the Durand Line, allowing Osama bin Laden to escape into Pakistan during the Battle of Tora Bora.