Today marks the 31st anniversary of the first attack on the World Trade Center. A van bomb detonated below the North Tower, killing six people, including 61 year-old Robert Kirkpatrick of Suffern, who worked in the towers as a Port Authority Senior Structural Maintenance Supervisor. The Port Authority of New York and New Jersey will hold a memorial Mass today at noon to commemorate the anniversary with a moment of silence at the Memorial North pool at 12:18pm. You can watch the ceremony live at 911memorial.org.