Brooks Koepka fired a 2-under-par 68 in the final round on Sunday to finish at 1-over-par 281 and capture the 118th U.S. Open Championship by a stroke over Englishman Tommy Fleetwood at the demanding Shinnecock Hills Golf Club in Southampton, N.Y.Koepka, who won last year at Erin Hills Golf Club in Wisconsin, became the first golfer to take back-to-back U.S. Opens since Curtis Strange accomplished the feat in 1988-89. Koepka is the seventh player to win America’s national championship of golf in back-to-back years.”It hasn’t sunk in yet. This is incredible,” Koepka said in a television interview. “You know, I don’t think I could have dreamed of this — going back-to-back. It’s truly special and I’m so honored.”Fleetwood carded a 63, becoming the sixth player to record that score at the U.S. Open and just the second to do it in the final round. He teed off almost 2 1/2 hours before — and six strokes behind — third-round leaders Koepka, Dustin Johnson, Daniel Berger and Tony Finau on Sunday and soared up the leaderboard with four consecutive birdies on holes 12, 13, 14 and 15.Fleetwood missed a nine-foot putt for birdie and a record 62 at the closing hole. His round was even more impressive considering he didn’t birdie either of the layout’s par 5s.Johnson, who was tied for the lead after the first round and four strokes clear of the field after 36 holes, finished alone in third two shots behind Koepka at 3 over after an even-par 70 in the final round.Reigning Masters champion Patrick Reed ended up fourth at 4 over after a 68 in the final round, while Finau (72) double-bogeyed the final hole to finish in fifth another stroke back at 5 over.Koepka trailed Johnson by six strokes after the first round and by five after the second round. He shot a 72 in nearly unplayable conditions on Saturday when Johnson stumbled to a 77 to climb back into the mix and was steady and often spectacular over the final 18 holes.Koepka racked up three birdies in his first five holes on Sunday to grab the championship by the throat but gave back a shot with a bogey on the sixth. A birdie on the 10th precluded a bogey on the 11th, but he likely clinched the win with a scrambling, one-putt par on the 14th after hitting his drive into the deep fescue to the right of the fairway.”It really, really was testing this week, to be honest with you,” Koepka said of the course.After Koepka holed his par putt there, Johnson three putted for bogey that all but ended his chances to put any pressure on Koepka down the stretch.