Mystik Dan won the 150th running of the Kentucky Derby in a heart-pounding three-horse photo finish on Saturday at Churchill Downs.

The bay colt trained by Kenny McPeek and ridden by Brian Hernandez Jr, who went off at 18-1 odds, held off Sierra Leone by a nose with the Japanese colt Forever Young a whisper behind in third, the closest finish to a Kentucky Derby in nearly three decades.

The crowd of 156,710 spectators waited nearly 10 minutes before the result was declared official. Catching Freedom placed fourth in the $5m race while the second runner from Japan, T O Password, took fifth.

“That was the longest few minutes I’ve ever felt in my life,” Hernandez said. “It was exciting when we hit the line, but I wasn’t sure if we won, it was quite a rush to sit there and wait for it.”

The upset marked the tightest margin in America’s most famous thoroughbred race since Grindstone edged Cavonnier in 1996 – and only the 10th time it’s been decided by a nose.

Additionally, it was the first three-horse photo finish in a Kentucky Derby since 1947, when Jet Pilot finished a head in front of Phalanx and one length ahead of Faultless. Saturday’s was even closer.

Early leaders Just Steel, Track Phantom and Fierceness, the morning-line favorite at 3-1, set the pace during the first half-mile over a fast track through fractions of 22.97sec and 46.63sec. That trio stayed in front through six furlongs (1min 11.31sec) and a mile (1min 37.46sec).

From there Hernandez became the difference-maker, shooting forward when Track Phantom momentarily drifted off the rail and opening a lead by the eighth pole. Sierra Leone and Forever Young closed side by side on the outside over the final eighth-mile, but Mystik Dan held on by the slimmest of margins in a winning time of 2min 3.34sec.

“My horse was so game being up on the inside,” the Louisiana-born jockey said. “I came through a really tight spot. We kind of climbed up on top of the rail a little bit. When he shot through that spot and he was able to cut the corner and I asked him to go for it, he shot off and I’m like, ‘Oh man, we’ve got a big chance to win the Kentucky Derby.’

“To see you number flash up to win the Derby like this, I don’t think it’s going to sink in for a while.”

Hernandez and McPeek had teamed to win the Kentucky Oaks for fillies barely 24 hours earlier with Thorpedo Anna. That made McPeek the first trainer since Ben Jones in 1952, and only the fourth ever, to win the Oaks and the Derby in the same year.

“Brian did an amazing job,” McPeek said. “He’s just a brilliant, brilliant, brilliant jockey. He probably one of the most underrated riders in the business. But not anymore.”

Mystik Dan, the Kentucky-bred son of Goldencents out of the Colonel John mare Ma’am, earned the $3.1m winner’s share of the record $5m purse. The three-year-old had punched his ticket for Saturday’s race with a third-place finish in the Arkansas Derby and a win in the Southwest Stakes, both at Oaklawn.

A rematch with Arkansas Derby winner Muth is likely in the offing in two weeks’ time in the Preakness Stakes, the middle jewel of US horse racing’s Triple Crown. Though McPeek didn’t commit on Saturday to the 18 May race at Pimlico, saying you “never make a decision until you absolutely have to”.

Fierceness, who won the prestigious Florida Derby prep race by a record 13-and-a-half lengths, finished 15th in the field of 20 entrants after hopping at the start and fading in the upper stretch.

Resilience took sixth, followed by Stronghold, Honor Marie, Endlessly, Dornoch and Track Phantom. West Saratoga came in 12th, ahead of Domestic Product, Epic Ride, Fierceness, Society Man, Just Steel, Grand Mo the First, Catalytic and Just a Touch.