Two runners didn't finish and another two were disqualified in a controversial men's 3000m steeplechase final.
Ugandan runner Jacob Araptany face-planted in one of the most brutal falls seen at the 2016 Olympics and failed to finish the race.
The 22-year-old tripped and stumbled at the worst possible moment, falling face-first into a barrier and then grinding his face beneath the jump marker in sickening fall.
After hitting the track hard he was unable to move as a field of runners desperately tried to avoid stepping on him while running past.
Araptany is reportedly recovering and did not receive any significant injuries. He was treated beside the track by medical officials.
The race was won by Kenyan Conseslus Kipruto, who stretched Kenya's stranglehold of the event to nine-consecutive gold medals in the men's 3000m race.
American Evan Jager won silver.
The bronze medal was awarded amid incredible controversy after Kenya's Ezekiel Kemboi was disqualified for stepping off the track hours after the race was won. The late protest promoted France's Mahiedine Mekhissi to bronze.