PHILADELPHIA, JULY 20 -- Sharmba Mitchell looked so happy in the ring tonight. It was all smiles and left hooks from the Washington lightweight, who dispatched with his latest challenger even more impressively than normal.

Mitchell floored Colombia's Freddy Sevilla in the first round and never relented, opening a deep cut under Sevilla's right eye that prompted his cornermen to ask referee Tom Reed to stop the scheduled 10-round bout after the fifth, giving the unbeaten Mitchell his 18th victory and eighth knockout in front of 500 -- including several friends who came here from Washington to see him -- at the Blue Horizon.

It was Mitchell's second fight in 17 days, yet the 19-year-old showed no signs of wear from his fifth-round technical knockout of Eric Podolak of Pittsburgh on July 3 at D.C. Convention Center.

Instead, Mitchell, ranked No. 12 by the North American Boxing Federation, started perhaps stronger than he ever has, stunning Sevilla (14-2) midway through the first round with a left hook, followed by another moments later that floored him.

"When he went down in the first round, I knew I could hit him after that," said Mitchell, who scrapped an earlier plan to slow down the pace because the humidity was so high. "He was slow, that was his main problem."

Although Mitchell was unable to finish Sevilla in the first round, he continued to score in the next few, repeatedly catching his opponent with a left hand that many have criticized Mitchell for using too sparingly. But there will be no criticism for this performance, which rivaled Mitchell's previous best showing, an eight-round decision victory over England's Nigel Wenton in April.

"{Sevilla} was supposed to be my toughest challenger," Mitchell said. "But I couldn't tell."

Said Sevilla cornerman Al Bonanni: "I think Freddy got cut and got concerned about his eye, and didn't get off. It looks like he needs about 15 stiches. The {ringside} doctor said the cut was not a problem" but it wasn't worth it.

It was Mitchell's second appearance in this historic building, which, despite a lack of air conditioning and other modern amenities, remains popular because fans can get close to the action. The best seats are the rickety wooden bleachers hanging just over the ring, giving spectators an opportunity to look down -- and yell loudly -- at the fighters.

"I feel very comfortable {here}," Mitchell said. "The Blue Horizon is just known for fighting hard.

"It's always more of a fight atmosphere in {Philadelphia}. They want to see blood."

Promoter Bruce Gelb said both fighters received a purse of "approximately $3,500 each."

After Mitchell's victory, Washington weltwerweight Keith Holmes (8-1) suffered his first pro defeat, losing a six-round decision to Ronnie Hammond (9-0-1) of Philadelphia.

District junior weltwerweight Elwyn Kemp (2-1) also lost in an undercard bout to Willie Rivera (7-1).