Vito Mielnicki Jr. didn’t hear cheers Saturday the way he did when he won his pro debut by scoring a sensational, first-round knockout in his native New Jersey four months ago.

The crowd booed when Mielnicki was announced as the winner of his fight against Marklin Bailey on the Deontay Wilder-Luis Ortiz undercard at MGM Grand Garden Arena. They weren’t jeering the 17-year-old welterweight prospect’s performance, though.

Many in the crowd expressed displeasure with referee Russell Mora for what they felt was a premature stoppage in their four-round, 147-pound fight.

Mora stepped in to halt the action 2:31 into the second round. Mielnicki had just hurt Bailey with a left hook and a right hand that sent a vulnerable Bailey stumbling backward, toward a neutral corner.

“I felt Bailey was hurt and the ref protected the fighter,” Mielnicki told BoxingScene.com. “I have no control over the officiating. It was great to get a knockout in my Vegas debut. I appreciate the platform PBC afforded me.”

Mielinicki, a senior at West Essex High School in New Jersey, improved to 3-0 and recorded his third knockout. The Nevada State Athletic Commission granted Mielnicki an exception for a boxing license at its monthly meeting Wednesday because professionals typically are required to be at least 18 to fight in Nevada.

Mielnicki, of Roseland, New Jersey, was extended beyond the first round for the first time since making his pro debut July 13 at Prudential Center in Newark, New Jersey. Each of his first two fights resulted in first-round knockouts.

The 25-year-old Bailey, of Durham, North Carolina, dropped to 6-6 (4 KOs).

Bailey landed a solid right hand in the first round that at least let Mielnicki know he had come to fight. Mielnicki became more comfortable in the second round, when he began opening up on Bailey.

Mielnicki landed a right hand that hurt Bailey and caused him to hold several seconds before Mora separated them and Mielnicki connected with the aforementioned combination.

In the fight following Mielnicki’s victory, junior welterweight prospect Omar Juarez knocked out Kevin Shacks with a picture-perfect, counter right hand in the sixth and final round.

Juarez’s punch landed directly in the middle of Shacks’ face and sent him to his gloves and knees. Shacks barely beat referee Vic Drakulich’s count, but Drakulich determined Shacks shouldn’t continue.

Drakulich stopped the action 1:59 into the sixth round.

The 20-year-old Juarez, of Brownsville, Texas, upped his record to 6-0 and produced his fourth knockout. Shacks, of Lansing, Michigan, slipped to 3-5-3 (3 KOs).

Keith Idec is a senior writer/columnist for BoxingScene.com. He can be reached on Twitter @Idecboxing.