The officers took cover and shot at the man, who retreated into a nearby home.
Police had the suspect surrounded and were evacuating the area, a source told the Times.
A polling booth at the Memorial Park North Recreation Centre is within a block of the shooting. It and several schools have been locked down. AAP reported that there was no indication the incident was election-related.
The sho9oting was reported around 11am NZ time.
Roberto Chavez, 67, was sitting on his porch when he saw a heavily armed man fire at least 10 rounds at a group of people.
Chavez told the Times that police quickly responded and around 20 officers swarmed into the neighborhood.
The gunman, who wore a white shirt and black pants, ran into a home about three doors down from Chavez' house, he said.
Chavez said he recognised the man as a frequent visitor to his neighbor's home. He didn't know the man's name. He said some of the victims appeared to be neighbours in the area.
He was told to stay indoors by police while the gunman is nearby.
"It's a very dangerous situation," he said.
Aerial footage reveals firefighters have set up red, yellow and green tarps on the street while Swat members converged.
A helicopter took at least one person to hospital.
Elizabeth Hopkinson told NBS Los Angeles she and her 9-month-old son were locked down at Slauson Middle School nearby. She said she was on her way to vote when the shooting happened.
She heard "pow, pows, then a rain of fire".
She said she was locked down with about 25 others in the gym.
Officer Jerry Willison of the Azusa Police Department told the Times there were civilian injuries.
"This is a very volatile and critical situation."
Nearby Slauson Middle School and Mountain View Elementary School were placed on lockdown, according to Fox11.
Azusa has a population of around 49,000.
