According to police, Johnson was the victim of a drive-by shooting and had been shot minutes earlier. Police said they rendered aid until emergency medical technicians arrived and transported Johnson to Danbury Hospital. Johnson was later pronounced dead, they added.
Police said Agramonte faces charges including murder, first-degree criminal attempt to commit assault, risk of injury to a minor and first-degree reckless endangerment.
Officials said Agramonte was already in the custody of the Connecticut juvenile detention system at the time of his arrest. Investigators anticipate more charges will be filed.
The incident remains under investigation. Anyone with information is asked to contact police at (203) 796-1601 or J.Williams@danbury-ct.gov. Anonymous tips can be left at 203-790-8477.