Body camera footage shows Janet Lockridge's 10-year-old daughter, Auria, leading Cappell to her mother's car, where her sister, Harleigh, was suffering from the life-threatening emergency.
"She was struggling for air, she was struggling to breath," Lockridge said.
As Cappell approached the car, the worried mother could be heard crying as she tried to figured out how to help her baby.
"I was afraid," she said. "I didn't know what the outcome was going to be, and I was just praying the whole entire time."
Cappell then "reverted back to his training" and grabbed the little girl, placing her face-down in his hands so he could give her some firm slaps on her back. To his relief, the method worked.
"Once I heard the baby crying, it was the best sound I ever heard in my life," he said.
The next day, Cappell posed with Harleigh, who had since recovered from the accident.
Cappell received special honors Monday to commemorate his life-saving actions, KABC reported.
Lockridge told the station that she is "extremely, extremely grateful" that Cappell was nearby to help save her daughter's life.
"I am, like, indebted to him forever," she said. "It was amazing. It was truly amazing."