Prince George's County prosecutors said yesterday that a 15-year-old boy was the "initiator" and "lead actor" in the death of Michael A. Bassett, a high school senior who was beaten, left on a busy road and run over by motorists outside a 7-Eleven after he offered to buy a Slurpee for a girl he did not know.

The suspect, Emmanuel A. McClain, who turned 16 yesterday, surrendered to police Wednesday and was charged as an adult with first-degree murder in the attack on Bassett, who was 18 and due to graduate next week from Oxon Hill High School. Authorities said McClain and Bassett were strangers when the incident occurred about 3:15 a.m. Sunday in the 5400 block of Silver Hill Road in Oxon Hill.

In Prince George's District Court, where McClain was ordered jailed without bail pending a June 14 preliminary hearing, prosecutor John Maloney said yesterday that a videotape from a store surveillance camera shows McClain "swinging" at Bassett.

Maloney said witnesses told police that McClain then led a group of youths who chased the victim onto the road and punched and stomped on him. According to a police affidavit filed in court, Bassett was left "incapacitated" on the road and was accidentally run over by two passing motorists. Police said Bassett did nothing to provoke the assault except offer to buy a Slurpee for a girl who was standing outside the store with friends.

"For some reason, this defendant took offense to that, and now Michael Bassett is dead," Maloney said in court. Calling McClain "a danger to the community," he said a security guard at Suitland High School, where McClain is a sophomore, described him to authorities as a youth who is "fascinated with the thug life and interested in guns, drugs and prison life."

Without elaborating, Maloney said McClain has a juvenile arrest record, is a member of "a street crew," has often failed to show up for classes at school and has been "suspended a couple of times for fighting." The prosecutor also alleged that McClain "robbed" Bassett of "several items" after the beating, but he did not specify what was taken.

McClain's arrest was the first in the case, and authorities said they are seeking several other suspects who witnesses said were involved in the attack on Bassett and two of the dead victim's friends, neither of whom was seriously hurt. The three had stopped at the 7-Eleven after a night of dancing, authorities said.

Although police charged McClain with first-degree murder, State's Attorney Glenn F. Ivey told reporters yesterday that McClain could wind up being charged with a lesser offense, depending on what authorities learn in their continuing investigation of the incident.

An autopsy found that Bassett died of multiple injuries, but it is unclear whether he was killed by the beating or from being run over, authorities said. Although in some cases a suspect can be convicted of murder for an unplanned death that results from another crime, it is not true in every instance, said Ramon Korionoff, an Ivey spokesman. He said investigators must further analyze the motives, intentions and actions of those involved in the attack.

McClain's attorney, Antoini M. Jones, told reporters after yesterday's bail hearing that his client played a "minor role" in the attack and did not instigate it.

"The prosecutors must have inaccurate information," Jones said. He said McClain and Bassett bumped into each other at the 7-Eleven, which led to a scuffle. He said that incident was separate from the beating in the street. He also said he plans to file a motion asking a judge to order McClain's case moved from adult court to juvenile court.

Jones said he opposed his client's surrender. He said he told McClain that authorities "did not have his name, did not have an arrest warrant. I said, 'If you turn yourself in, they will know your name . . . and there's a real possibility you will be in jail till your trial date.'"

According to the police affidavit, McClain was identified through tips, the surveillance video and witness accounts. The affidavit states that after Bassett offered to buy a Slurpee for the girl outside the 7-Eleven, McClain confronted him in the store. Police said the assault occurred even though Bassett apologized for speaking with the girl.

Michael A. Bassett died after being beaten, left on a road and run over by motorists outside a 7-Eleven.Defendant Emmanuel McClain is on closed-circuit TV as attorney Antoini Jones, far right, and prosecutor John Maloney talk to Judge Patrice Lewis.