US man Kyle Burgess got more than he bargained for when he went for a run in Slate Canyon, Utah.
Video posted to Burgess' Twitter account shows two cougar cubs appearing ahead of him on the trail. Then mum shows up - and she's mad.
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Just seconds after Burgess' cub sighting, the cubs' mother emerges from the undergrowth and begins to walk towards him, hissing and lunging.
Burgess is clearly terrified in the video. "C'mon dude! I don't feel like dying today," he yells as the cougar growls.
"This is scary. My heart is racing. Dude, ok. This is not fun. Go away! Go away! Go back to your babies!"
The encounter lasts for six terrifying minutes, before Burgess throws a rock at the cougar and it retreats.
In an interview with KSL Newsradio, Burgess said he had been trail-running for years but had never encountered a cougar before.
"Right as I knew what she was, a cougar coming up on me, I decided I needed to get away from her babies," he said.
Following the advice of hunters, he chose not to run from the cougar, to make himself look as large as possible and to make loud noises.