AZUSA, California (Jason Kandel, NBC) -- A shooter opened fire in a residential neighborhood in Azusa on Tuesday, injuring four people, pinning down arriving officers who were met with gunfire and locking down a polling place.

The incident was reported at 2:05 p.m. at West Fourth Street and North Orange Avenue, officials said.

Aerial footage showed firefighters setting up red, yellow and green tarps in the street while members of a SWAT team converged in a neighborhood.

A Los Angeles County Sheriff's Department helicopter took at least one person to a hospital.

Elizabeth Hopkinson said she and her 9-month-old son were locked down at Slauson Middle School nearby. She said she was going to drop off her mail-in ballot when the shooting happened.

She said she heard, "pow, pows, then a rain of fire."

She said she was locked down with about 25 others in the gym.