ARLINGTON, Texas (AP) — WBC champion Jose Ramirez delivered a series of punches to the head of WBO champion Maurice Hooker, who was pinned against the ropes and taking a pummeling when the referee stepped in and stopped the world super lightweight unification bout in the sixth round Saturday night.

Ramirez connected on two lefts to the head of Hooker, knocking the stunned hometown fighter into the ropes. The WBC champion from California then kept punching until the scheduled 12-round bout was stopped by referee Mark Nelson.

It was the third title defense for Ramirez, who improved to 25-0 with his 17th knockout. His first two title defenses came at home in California.

Hooker dropped to 26-1. It was his third title defense, the first at home for the 29-year-old from Dallas known as "Mighty Mo."

Ramirez, the 2012 Olympian who took the vacant WBC title in the 140-pound division in March 2018, had a flurry of punches in the opening round that sent Hooker stumbling into the ropes. He stayed up then, but Hooker did go down soon after that after landing a blow but taking a counterpunch and being unable to keep his balance when Ramirez was standing on his foot.

Both fighters landed solid blows in the second round, but Ramirez again had Hooker against the ropes, with the hometown favorite mostly covering up. But when the ref stepped in between them at the end of the second round, Hooker had a smile on his face and was talking toward his opponent while going to the corner.

The third and fourth rounds both ended with the fighters exchanging punches and having to be separated by the referee when the bell rung.

Before the main event, there was a memorial 10 count of the bell for 1984 Olympic gold medalist and four-division champion Pernell "Sweet Pea" Whitaker and two fighters who died this week after bouts last weekend.

Whitaker died earlier this month after being hit by a car in Virginia. He was 55.

Maxim Dadashev died Tuesday from bleeding in the brain, four days after the Russian went 11 grueling rounds in Maryland. Then on Thursday, Hugo Santillan, a 23-year-old Argentinian, five days after collapsing following his super lightweight bout.

Both title fights on the undercard went the distance and ended with unanimous decisions.

Tevin Farmer defended his IBF world super featherweight title for the fourth time in less than a year in 12 rounds against over mandatory challenge Guillaume Frenois. Tramaine Williams beat Yenifel Vicente in a 10-rounder for the vacant USBA super bantamweight title.

Farmer took the vacant IBF title last August, and is 30-4-1 after the matchup of southpaws. Frenois, who is from France, lost for only the second time in 49 pro fights (46-2-1).

Williams, the 122-pound "Mighty Midget" from Connecticut, overcame a couple of low blows that deducted points from Vicente. There was a lengthy pause after one such shot in the middle of the seventh round, but Williams rebounded with a flurry of punches and went on to improve to 19-0. Vicente dropped to 35-4-2.