John Hetlinger left the Navy pilot ranks for aerospace engineering. He succeeded in that field, working for NASA on the Hubble Space Telescope for NASA before retiring in his late 60s.
That's when he got into karaoke, singing at karaoke bars in pleated shorts and pants and nice polo shirts. He's apparently got a thing for polos with toucans, which is kind of sweet.
Oh, but the songs he sings are heavy metal, and Drowning Pool's "Bodies" appears to be one of his favorites to perform:
That's Hetlinger on his recently aired episode of "America's Got Talent" where he wowed the judges with his performance. You can see Hetlinger perform a longer version of the song, where he includes some profanity, in this 2014 show from when he was a spry 80 years old.