According to the PGA Tour, nobody had managed the feat since accurate records of such occurrences began in 1983.
The low-key Reavie took the achievement in stride.
"It was strange," the 37-year-old American told Golf Channel at Waialae Country Club in Honolulu, where he trailed leader Matt Kuchar by four shots.
"You hit good shots and you don't expect them to go in. You're always surprised when they drop."
Reavie, the 2008 Canadian Open champion, wasted no time notching his first eagle, holing out from 100 yards at the 10th, his first hole of the day.
He added his next eagle from 150 yards at the 16th, and as if that was not enough made another from 135 yards at the sixth hole.
He said it was only after the third eagle that he started to wonder if a fourth was in store, and when his wedge approach at his 17th hole flew straight towards the pin he "thought could it really happen again".
His ball stopped six feet short of the cup.
Under the circumstances, he might have had reason to be slightly disappointed with a five-under-par 65, which included a double-bogey, but was not complaining.
"You can't be disappointed out here," he said after signing for a 10-under 130 halfway total.
"This golf course is tough."
(Reporting by Andrew Both in Cary, North Carolina; Editing by Greg Stutchbury)