Amid roiling smoke, the roar of the 40 machines' engines, and the waving of a red flag which signalled 'clear course ahead', American Johnny Aitken, in a National, took the lead from the fourth starting spot on the extreme outside of the first row, and held it until lap 5 when Spencer Wishart took over in a Mercedes, himself soon overtaken by David L. Bruce-Brown's Fiat which would go on to dominate the first half of the race. Sadly on lap 12 tragedy would strike as Sam Dickson (the riding mechanic for Arthur Greiner) was the first person killed in history during the Indianapolis 500. One of the front wheels came off the American Simplex car Greiner was driving, causing him to lose control and both men to be thrown from the car. While Greiner escaped with a broken arm, Dickson flew into a fence 20 feet (6.1 m) from the car. Reports state that Dickson was killed instantly, although the crowd evidently swarmed around the body, requiring the state militia who were acting as security at the event to use their guns as clubs to clear a path for the attending doctors. Nearing the halfway point, Ray Harroun, an engineer for the Marmon-Nordyke company and defending AAA national champion, and the only driver competing without a riding mechanic due to his first-ever-recorded use of a cowl-mounted rear-view mirror, passed Bruce-Brown for the lead in his self-designed, six-cylinder "Marmon Wasp" (so named for its distinctively sharp-pointed, wasp-like tail).