A man seated in his car was fatally shot by a gunman in another vehicle, according to the sheriff's department.

The shooting occurred about 5:45 p.m. Friday in the 170 block of East Payson Street, said Deputy Erin Liu.

The man was shot once in the chest and transported to a hospital, where he was pronounced dead, Liu said.

His name was withheld pending notification of next of kin.

The sheriff's department is assisting Azusa police in the homicide investigation, Liu continued.

A motive for the attack was unknown.

The sheriff's department has no suspect or vehicle description of the shooter.