Discription of Events: This driver tailgated me for approximately 2-3 miles while I was going the speed limit and he clearly had the ability to legally pass me on GW Parkway, near the chain bridge road entrance towards I-495 N. He eventually passed then proceeded to cut in front of me and slam on his brakes abruptly, causing me to slam on my brakes, which then caused 3-4 cars behind me brake as well. This driver put nearly 4-8 people at risk of crashing this morning around 8:25-8:45 AM.