"Not many people can say they've accomplished such an incredible feat—especially not at 71!" they captioned the post.
In the video, Pa'at is seen shuffling towards the trail-end marker as he gently sings to himself.
"I've been waiting… such a long time," he sings. "Walking such a long way. Such a long way… just to be here, just to be here. Across deserts. I walked through rivers, I climbed mountains, just to see you. Just to see you. I've been waiting. Such a long time."
A long-time, according to Pa'at, was five and a half months. Replying to a comment on the video, the hiker said he began walking on March 17 and completed the trail on August 30.
"My wife did 1800 miles with me," he added.
The video has been viewed more than 650,000 times in just two weeks.
Dozens of people commented on the video and said Pa'at's story had inspired them to attempt the walk or similar feats.
"I wanted to walk this trail a long time," someone wrote, "but now I know even if I don't get it in my twenties or thirties I can still try and try again!"
Others were simply moved by his achievement.
"Why is it that when I listen to this again..& again it brings me to tears," wrote one viewer.
"The world needs way more people like him," another added.
One person asked what song he was singing but fellow viewers suggested it was one Pa'at made up.
Auti and Chris first met Pa'at in Stehekin, Washington, 80 miles from the Northern Terminus, which marks the end of the trail.
"We only knew him a few days before finishing, but he's one of those people you instantly feel like you've known a lifetime," they said.
"He has a heart of gold, the kindest soul, and unmatched optimism and fortitude. Thank you for being such an inspiration to us, Pa'at!"
