BROOKLINE: Canada’s Adam Hadwin birdied five of the last six holes on the front nine and seized a one-stroke lead after Thursday’s first round of the US Open with Rory McIlroy in a pack one adrift. World number 105 Hadwin, whose best finish in 19 prior major starts was a share of 24th at the 2018 Masters, fired a six-under par 66 at The Country Club. Four-time major winner McIlroy, who tossed one club and twice swung another at sand in frustration, shared second on 67 after a closing bogey with Sweden’s David Lingmerth, England’s Callum Tarren, American Joel Dahmen and South Africa’s M.J. Daffue. Hadwin, whose only PGA title was at the 2017 Valspar Championship, missed a six-foot par putt to bogey the third hole, then birdied five of the next six holes, dropping his approaches between two and four feet on all but the par-3 sixth and making each short birdie putt to grab the outright lead. The 34-year-old Canadian missed the green at 12 on the way to a bogey but holed out for birdie at 13 from the rough from 36 feet to reclaim the lead. Back-nine starter McIlroy rolled in four birdie putts between 10 and 25 feet and made several long clutch par-saving putts, notably at the fifth from 14 feet after failing to escape a bunker and smashing sand with his club. McIlroy, who won last week’s PGA Canadian Open, has not captured a major title since the 2014 PGA Championship. Two-time major winner Dustin Johnson, among the rebels who left the US PGA Tour for the Saudi-backed LIV Golf Series, led a seventh-place pack on 68 that included fellow Americans Hayden Buckley, Matthew NeSmith, Aaron Wise, Brian Harman plus England’s Matthew Fitzpatrick and Justin Rose.