The acting supervisor of the motorcycle unit of the Prince George's County Police Department killed himself early Sunday morning after making a routine radio call requesting that homicide investigators meet him in Upper Marlboro, officials said yesterday.

Cpl. Melvin Anthony Brown, 40, a 14-year member of the force, was found dead about 1 a.m. Sunday near the entrance to the Equestrian Center in Upper Marlboro, police said.

The death was ruled a suicide after an autopsy by the state medical examiner's office determined that he died of a gunshot wound in the head. Before shooting himself, police said, Brown set himself on fire. An investigation is continuing into the reasons for the suicide.

Lt. John Moss, a police spokesman said Brown was found dead by a beat officer responding to the corporal's call for investigative assistance. Brown had said he was at a crime scene, but police said there was no evidence of a crime.

"When the officer got to the crime scene, the scene was the death" of Brown, who was dressed in his full motorcyclist's uniform, said Moss. Brown was off duty and his police cruiser was found at the scene, officials said.

The suicide jarred members of the department who said that Brown's affable and professional manner belied whatever tensions may have led him to kill himself.

"Until Friday he was just as bubbly and as energetic as he was his first day in the motorcycle unit," said Lt. William Lowry, who as commander of special enforcement operations was Brown's immediate supervisor.

Police said that Brown had a passion for motorcycles. He had been in the motorcycle unit since its formation 11 years ago and last year was named the best motorcyclist in the eastern region by the Mid-Atlantic Police Officers' Motorcyle Association.

Brown extended his love for motorcycles to others in the force. "He would work with you to overcome whatever hurdles you might face in learning how to ride a motorcycle," Moss said, adding that he never heard Brown criticize colleagues. "He found he got more done with a little sugar rather than salt," said Moss.

Brown was the only corporal in charge of a departmental unit, a command he was given nine months ago to replace a departing sergeant, officials said. Lowry said Brown had received some 30 letters and commendations praising his work in the last 18 months.

Brown was a six-year veteran of the Marine Corps and had served in Vietnam. He is survived by a wife, daughter and granddaughter. Police, at the request of the family, would not release their names.