Unfortunately I cannot get a link of the video to post, but Road &Track reports there was a spectator walking on track, alongside the armco on lap 37 of the race.
The incident brought out initial confusion as to why a safety car was dispatched, but no one was aware of an on track accident at first, and he seemed to walk quite a distance up track, off the racing line it seems, before spotted by the marshalls.
No initial explanation as to why he leisurely strolled onto the course, but one wonders as to why, he did, and this a being night race, avoided being hit. smh...
If any of my fellow members are able to provide the link or video, I'd appreciate it.