Oakmont, Pa. (AP) -- Dustin Johnson had everything going his way Sunday in the U.S. Open.
He was playing the best golf on the toughest course. He had a two-shot lead on the back nine at Oakmont. He even got a huge break on a ruling that allowed him to escape deep rough, the kind of breaks that usually go to major champions.
That's when he saw two USGA officials approach him on the 12th tee. They told him he might get a one-shot penalty for his ball moving on the fifth green. They wouldn't know until after his round.
Try playing the back nine of a U.S. Open with that kind of confusion.
"It's nothing new at this point," said Johnson, who has had major mishaps for the last six years. "It's happened so many times I kind of expect it now."
The difference was the outcome.
Johnson showed the mettle — and yes, the wits — to finally win a major championship.
"For it to not affect the outcome is fantastic," he said. "It just shows how well I played."
No one knew if he was leading, tied or one shot behind, and neither did Johnson. He didn't look at a board the rest of the day, taking on each shot regardless of the score and coming up with all the right shots — the 10-foot par save on the 16th, a cautious bunker shot on the 17th, and a 6-iron that settled the score. It dropped down 5 feet from the hole for a birdie that wrapped up a U.S. Open that was overdue.
The USGA wound up giving him the penalty shot after it was over, so Johnson closed with a 1-under 69 for a three-shot victory over Shane Lowry, Scott Piercy and Jim Furyk, a runner-up at Oakmont for the second straight U.S. Open.
"I still didn't want the penalty. I didn't think that I did anything to cause the ball to move," Johnson said. "But at the end of the day, it didn't affect what happened. So it doesn't bother me at all."
Finally, he's a major champion.
Johnson scooped up 18-month son Tatum into his arms on Father's Day and raised the silver trophy for all to see.
"I've been here a bunch of times and haven't quite got it done," Johnson said. "But today, I did. And it feels really good."
He saluted a Pittsburgh crowd that was on his side even amid all the uncertainty. The grandstands were raucous, with one fan shouting, "What's the call, USGA?" At the trophy presentation, when Fox Sports announcer Joe Buck brought up the penalty situation, the crowd booed.
Johnson finished at 4-under 276, the lowest winning score in nine U.S. Opens at Oakmont.
The lingering question was whether the toughest test in golf was tougher than it needed to be.
Johnson had a short par putt on the fifth hole, took a few practice strokes and as he placed the putter behind the ball, it moved slightly — backward. Johnson stepped back and called over the rules official, told him he didn't cause it to move. He tapped in for par.
Jeff Hall, senior director of rules and open championships for the USGA, said a staff member said on the radio that it might be worth another look. The USGA thought Johnson should know that his score might be one shot worse than it was, so it told him on the 12th tee.
"After looking at video, the actions he took could have caused the ball to move," Hall said. "We asked if there was some other reason the ball could have moved. He didn't state a reason."
But it led to confusion over the entire back nine — for Johnson and for the guys trying to catch him.
Lowry, who began the final round with a four-shot lead that he lost on the front nine, tied him when Johnson made bogey on the 14th.
Were they tied? Was Johnson trailing by one?
Jack Nicklaus, who won the first of his 18 majors at Oakmont in 1962, said if the USGA thought it might be a one-shot penalty, it should have done it right there and "let him get on with the job."
That's what he did, scrambling for pars, keeping his cool, thinking only the major that kept eluding him.
Johnson said he couldn't help but wonder if he was in for more bad luck at a major that he was poised to win.
"Just one more thing to add to the list, right?" he said.
The most painful was last year in the U.S. Open at Chambers Bay, when Johnson had a 12-foot eagle putt to win and three-putted for par to lose by one to Jordan Spieth. There also was that two-shot penalty at Whistling Straits that kept him out of a playoff in the 2010 PGA Championship when Johnson grounded his club in sand without realizing it was a bunker. He was chasing down Darren Clarke in the 2011 British Open when he hit a 2-iron out-of-bounds on the 14th hole. He lost a three-shot lead at Pebble Beach in the 2010 U.S. Open by closing with an 82.
Not this time.
Lowry became the first player since Payne Stewart at Olympic Club in 1998 to lose a four-shot lead in the final round of the U.S. Open. He made birdie after being told of the potential Johnson penalty, but the Irishman lost his putting touch with three-putt bogeys on three straight holes. He closed with a 76.
Lowry and all the other players on the course were informed that Johnson might get penalized after his round.
"It didn't affect the way I played," Lowry said. "If anything, I credit Dustin for playing the way he played on the way in, having that hanging over him, because I probably would have wanted to know straightaway if it was me."