He snapped the photo just as a man emerged from behind a car and fired at him.
Family members turned the image over to police and officers arrested the shooter and an accomplice.
Police said the shooting was revenge for an earlier incident in which Dagsa ordered the suspect arrested for car theft.
The family members said they did not hear a gunshot because New Year's firecrackers were exploding all around them. They only saw Dagsa falling to the ground after he was hit.
They said they rushed him to the hospital but it was too late.
Local police said that Dagsa was shot as he pressed the shutter of his camera.
Police described 38-year-old Dagsa as a hardworking councilman who was tough on crime.
The Associated Press contributed to this report.