Officials have released no suspected motive for the alleged slaying

A 15-year-old Fallbrook boy was arrested this week on suspicion of fatally shooting his older brother, authorities reported Friday.

The teenager, whose name was withheld because he is a minor, was taken into custody Thursday for allegedly killing 24-year-old Eduardo Delarosa a day earlier, according to the San Diego County Sheriff's Department. The boy was booked into juvenile hall in San Diego on suspicion of murder.

Deputies responding to a report of an assault about 8:30 p.m. Wednesday found Delarosa lying in front of a home in the 900 block of Alturas Road, in Fallbrook, suffering from a gunshot wound to his abdomen, sheriff's Lt. Michael Krugh said. Paramedics took the victim to a hospital, where he was pronounced dead.

Officials have released no suspected motive for the alleged slaying.

"Sheriff's homicide investigators are working to gather more information to determine the circumstances and motivation behind this death," Krugh said Friday.