Graham became the fourth private citizen to lie in honor in the Rotunda. On September 24, 2015, Pope Francis gave a joint address to Congress, the first Pope to do so. Security The U.S. Capitol is believed to have been the intended target of United Airlines Flight 93, one of the four planes that were hijacked on September 11, 2001. The plane crashed near Shanksville, Pennsylvania after passengers tried to regain control of the plane from the hijackers. Since the September 11 attacks, the roads and grounds around the Capitol have undergone dramatic changes. The United States Capitol Police have also installed checkpoints to inspect vehicles at specific locations around Capitol Hill, and have closed a section of one street indefinitely. The level of screening employed varies. On the main east–west thoroughfares of Constitution and Independence Avenues, barricades are implanted in the roads that can be raised in the event of an emergency. Trucks larger than pickups are interdicted by the Capitol Police and are instructed to use other routes. On the checkpoints at the shorter cross streets, the barriers are typically kept in a permanent "emergency" position, and only vehicles with special permits are allowed to pass. All Capitol visitors are screened by a magnetometer, and all items that visitors may bring inside the building are screened by an x-ray device. In both chambers, gas masks are located underneath the chairs in each chamber for members to use in case of emergency. Structures ranging from scores of Jersey barriers to hundreds of ornamental bollards have been erected to obstruct the path of any vehicles that might stray from the designated roadways. After the January 6 United States Capitol attack, security increased again. Additional security fences were installed around the perimeter, and National Guard troops were deployed to bolster security. List of security incidents On January 30, 1835, what is believed to be the first attempt to kill a sitting President of the United States occurred just outside the United States Capitol. As President Andrew Jackson was leaving the Capitol out of the East Portico after the funeral of South Carolina Representative Warren R. Davis, Richard Lawrence, an unemployed and deranged housepainter from England, either burst from a crowd or stepped out from hiding behind a column and aimed a pistol at Jackson which misfired. Lawrence then pulled out a second pistol which also misfired. It has since been postulated