Team Penske driver McLaughlin and Andretti Autosport’s Grosjean were battling over the lead after the final round of pitstops, having earlier almost come together at Turn 4 after the first pitstop sequence.
With 28 laps to go, leader McLaughlin emerged from the pits on cold tyres, with Grosjean – on recently changed and fresh hot rubber – right behind him. As they charged towards Turn 4, Grosjean attempted to outbrake him around the outside but McLaughlin also went deep under braking, locked his rears and took them both out into the tyre barrier.
