The first Chicago firefighter to die this year while on duty was killed in a fire that police are blaming on a 4th of July rocket. Firefighter James E. Hill, 44, died in the fire, and three other firefighters were injured, one seriously.

Hill, a nine-year veteran of the Chicago Fire Department, died at Cook County Hospital of burns and smoke inhalation, said department spokesman Jerry Lawrence. Hill, who was married with three children, was assigned to Engine Co. 49 of the 15th Battalion. Investigators believe the fire began late Saturday when a bottle rocket was fired into an open attic window. Where, neighbors said, boxes of books and old clothing had been stored in.

An alarm was sounded at 10:13 p.m., and four trucks from the 15th Battalion responded. Damage to the 2 1/2-story brick building was confined to the roof and attic, but a build-up of combustible gases in that area may have contributed to the firefighters injuries.