Associated Press Nancy Blanchard, an employee at a suburban Boston ice rink, testifies Monday in Cambridge, Mass., during the trial of Thomas Junta. Junta is accused of beating Michael Costin to death after the two argued over rough play at their 10-year-old sons' July 2000 hockey practice.

CAMBRIDGE, Mass. - A woman who witnessed the fatal fight between two hockey dads testified yesterday that she screamed, "Stop, please stop!" as one man continued to pound the other into unconsciousness.

Thomas Junta, 44, is accused of pummeling Michael Costin to death after an argument over rough play at their sons' hockey practice on July 5, 2000. Costin, 40, never regained consciousness and was pronounced dead the next day.

"I remember yelling to Mr. Junta, 'He's not responding, he's not responding. Don't hit him any more,'" said Virginia Brings, whose grandchildren were at the skating rink.

Junta said he was defending himself. But prosecutors say Junta, a 270-pound truck driver, used his size to overpower the 160-pound Costin and then pounded his head on the floor until he lost consciousness.

The prosecution rested its case yesterday, and the defense began by questioning an ice skating instructor who was at the rink during the fights. Junta's son took the stand at midday.

During cross-examination of Brings, defense attorney Thomas Orlandi Jr. questioned whether she was certain of the number of punches Junta threw, given that she was so upset.

"It's something that I'll never forget. He went on and on," she said without hesitation." I remember thinking at the time: He's either going to kill this man or he's going to have brain damage."

Earlier yesterday, a college hockey player who helped pull Junta off Costin testified that Costin threw the first punch and that Junta appeared to stop hitting him when Costin made a defensive move.

Ryan Carr, 21, said Costin put up his hand after Junta landed about three punches to Costin's head.

Orlandi asked Carr if Junta then instantaneously stopped hitting Costin.

"He appeared to stop, yes," Carr said.

His jaw trembling, Junta bit his lower lip and wiped his eyes with a tissue when Carr described how Junta left the rink and sat outside, waiting for police.

On Monday, Carr testified that Junta overpowered Costin and pinned him to the floor before he punched Costa. When Costin began shielding his head, "Mr. Junta pushed Mr. Costin's head into the mat."

Witnesses agreed that the two men initially scuffled briefly and then later had a second, more violent fight. Their testimony differed on exactly what happened in the second fight.

Rachel Labarge, a 12-year-old who was to take a figure skating lesson that day, was the first of several children expected to take the stand. She testified Monday that she saw the two men arguing and shoving each other.

She said Junta started to leave the building after the shoving but turned around before going out the front door. She said Junta tackled Costin and threw him to the ice.

"There were several punches to the face," Rachel said. "I saw about three ... He was pretty much straddled over Mr. Costin."

Composed throughout her testimony, the girl did not waver when Orlandi asked if she was sure of what she saw.

Other witnesses said Junta went into the parking lot before returning to the building, rather than turning back at the front door.

The trial has focused a national spotlight on the issue of parental violence at youth sports.

Rink employee Nancy Blanchard described being shoved aside by Junta as he re-entered the arena after the first fight and set upon Costin.

Blanchard said she saw Junta hit Costin at least six or seven times.

Junta "put his left knee on Mr. Costin's left shoulder," Blanchard said, choking up as she spoke. "He had (Costin's) head in his left hand. He was punching Mr. Costin's head and neck repeatedly."

"I think I remember screaming, 'You're going to kill him,'" she said.