A 15-year-old boy accused of being part of a group that beat and stabbed six men at last weekend's San Diego's gay pride celebration pleaded not guilty Friday to assault, robbery and hate crime allegations.The teen is one of four people charged in connection with the attacks about 10:45 p.m. Saturday in Balboa Park.Prosecutors want to try him as an adult, said Deputy District Attorney Oscar Garcia.James Allen Carroll, 24, and Lyonn Taz Tatum, 18, each pleaded not guilty Thursday to five counts of assault with a deadly weapon, one count of conspiracy to commit robbery and hate crime allegations. Carroll also was charged with two counts of attempted murder.Kenneth James Lincoln, 23, was charged with three counts of being an accessory after the fact.Prosecutors say the others gathered at his apartment before and after the attacks. They also say Lincoln shaved Tatum's head and put tattoos on him after the attacks in an effort to conceal his identity.During a brief detention hearing Friday, the 15-year-old pleaded not guilty to six counts of assault with a deadly weapon, one count of conspiracy to commit robbery and hate crime allegations."He was with the other two when they armed themselves with a baseball bat and a knife," Garcia said outside Juvenile Court. "He was clearly part of the attacks."Defense attorney Robert Bourne told reporters that he spoke briefly with the boy's mother."She's shocked," Bourne said outside Juvenile Court.He said prosecutors may have accused the defendants of committing hate crimes because the beatings occurred on the day of San Diego's gay pride celebration."It may not have been a hate crime," he said.The attacks happened as a large crowd was leaving the daylong San Diego Lesbian Gay Bisexual Transgender Pride Festival.Prosecutors said the defendants shouted anti-gay epithets during the attacks, and that witnesses heard Carroll and Tatum talk about robbing people to get money for drugs and alcohol.Witnesses said two of the defendants "viciously" attacked a man, hitting him in the shoulder with a bat, Garcia said. They also said Carroll, Tatum and the juvenile "savagely beat" other victims near the Lawn Bowling area in the park.The most seriously injured victim, Oscar Foster, was hit in the head and upper body 10 to 12 times, Garcia said.He remains in the hospital with a fractured skull and will have reconstructive surgery on his face, the prosecutor said.As people tried to get the defendants off the victims, another man was hit in the head five times.When one person called for help, Tatum stabbed him in the back of the shoulder, the prosecutor said.As the defendants ran from the scene, they kicked and beat another man, Garcia said.Investigators are looking into whether the attacks were gang-related, Garcia said. Police said the suspects apparently are members of a "wannabe" street gang called the "Low Lifes."Judge Andrew Kurz ordered the 15-year-old held at Juvenile Hall pending his next court appearance on Aug. 23.