The officers were attempting to speak with a group of people about the report when they all started to run away.
During the chase, an officer shot a man in the upper body.
The wound wasn't believed to be life-threatening.
One of the man's relatives said they were all gathered for a children's birthday party.
Authorities said a handgun was recovered at the scene of the shooting.
The Los Angeles County District Attorney's Office is investigating.
The Associated Press and City News Service contributed to this report.
