COSTA MESA — Moments after scoring a thrilling fourth-round knockout, Argenis Mendez climbed the turnbuckle in a corner and shouted in jubilation at the crowd.

He banged at his chest after winning the IBF junior lightweight championship from Juan Carlos Salgado. A  bit later, Mendez became more emotional because he knocked out Salgado in The Hangar at the O.C. Fair on Saturday night in front of 1,210.

"This is a very special moment," Mendez said with tears in his eyes. "I worked hard for this. I'm very excited and emotional about this win."

Saturday's main event came earlier for a live broadcast on HBO Latino. It also ended a bit earlier than expected. When Mendez and Salgado met in September, 2011, Salgado of Mexico scored a victory by decision.

Before Saturday's fight, Salgado said he wanted to leave no doubt this time in the 12-round bout. But it was Mendez who scored the convincing victory.

Mendez (21-2 with 11 KOs) knocked down Salgado (26-2-1 with 16 KOs) with a solid right in the first round. It quickly became evident Mendez had more speed than Salgado.

"He hit me good in the first round," Salgado said. "But I felt I could recuperate. But the referee took precautions and called the fight [in the fourth round]."

Mendez displayed great confidence during the fight, especially in the third round. When the boxers locked at one point in the center of the ring, Mendez whispered something in Salgado's ear. Mendez smiled, nearly laughing after they released.

Later, 45 seconds into the fourth round, Mendez connected with a devastating left hook to knock out Salgado.

"I came for the KO," Mendez said. "I knew if I hit him with a clean shot he would go down."

For the past 10 months, Mendez said he trained for the fight against Salgado.

"We prepared for the unexpected," Mendez said.

It definitely wasn't what Salgado was expecting.

The welterweight bout featuring Javier "El Intocable" Molina and Joseph Elegele also didn't disappoint for HBO Latino. Molina and Elegele went the full eight rounds, with Molina winning by unanimous decision.

Molina had a strong backing from the crowd, who continually chanted his name throughout the fight. Molina used  a series of power punches to come out on top.

He was proud of his win.

"I'm coming from the highest of highs from my [U.S.] Olympic days and to the lowest of the lows with [arm injuries]," he said. "And this is my best victory yet."

Molina's twin brother, Oscar, won in his U.S. debut, beating Willie Walton in the second round with a TKO in the welterweight bout.

Cornelius "Da Beast" White (21-1 with 16 KOs) defeated Otis Griffin (24-12-2 with 10 KOs) by unanimous decision in the 10-round light heavyweight bout.

Brandon Bennett scored a victory by unanimous decision against Mario Hermosillo in a six-round super lightweight bout.

Juan Funez of Van Nuys won in his pro debut, beating Jose Garcia in a four-round featherweight bout.

Immanuwel Aleem (3-0, 2 KOs) remained undefeated with a unanimous decision victory against Leshon Dante Sims of Inglewood in a four-round super middleweight bout.

Moshea Aleem scored a victory by unanimous decision against Dante Spinks in a four-round junior middleweight bout.

In a welterweight bout, Justin DeLoach won with a third-round knockout against Sail Fernandez.

Micky Roman scored a unanimous decision victory against Miguel Mungia in a welterweight bout.

steve.virgen@latimes.com

Twitter: @SteveVirgen