He's pretty studly with pbs of 1:46.70 and 3:37.22 but gold was certainly a surprise.
He had a sick last 200. Went from 4th to 1st. I timed in in 25.9 (54.7 last 400).
Race video:
https://www.youtube.com/watch?v=rzOUWGCPz0Q
Results
1 VILLARREAL PEINADO Jose Carlos MEX 5 OCT 1997 10 3:39.93
2 GREGOREK John USA 7 DEC 1991 3 3:40.42
3 PAULSON William David A CAN 17 NOV 1994 13 3:41.15
4 CATROFE CACHARRON Santiago URU 13 FEB 1999 4 3:43.17 (.164)
5 BRUNO Federico ARG 18 JUN 1993 1 3:43.17 (.167) SB
6 DE OLIVEIRA SANTOS Carlos BRA 9 JAN 1990 6 3:44.47 SB
7 MARTINEZ ESTRADA Fernando Daniel MEX 30 MAY 1993 2 3:45.13
8 HERNANDEZ SAMACA Carlos Santiago COL 29 JUL 1998 8 3:45.35 PB
9 LACAMOIRE Diego Javier ARG 9 MAY 1998 11 3:45.36
1ARROYO DOMINICCI Andres Gabriel PUR 7 JUN 1995 7 3:47.42
11 MINORS Dage Teako BER 26 OCT 1995 12 3:48.85
12 DÍAZ DEL RÍO Carlos Martín CHI 9 JUL 1993 5 3:49.33
13 GREGORIO DIANO Eduardo URU 4 JAN 1989 9 3:49.66
Intermediate Times: 400m 58.75 646 GREGOREK John (USA)
800m 1:59.13 646 GREGOREK John (USA)
1200m 2:58.13 72 BRUNO Federico (ARG)