The "Hart of Dixie" star was not in the car with her son, James Knight, at the time of the incident, authorities said.
Police said they responded to a call on Wednesday about vehicle vandalism in involving two cars.
The first car, police said, was occupied by a male adult driver and was "stopped at the apron of a driveway when the suspect kicked the vehicle causing damage."
The second car contained an unidentified friend of King's and the child. It was parked when the suspect allegedly jumped on it.
"The four-year old child was secured in a child car seat positioned in the back seat of the vehicle as the suspect jumped on the rear windshield causing glass to shatter and strike the child," the police report said. "In an effort to protect the child, the female driver exited the vehicle and confronted the suspect at which time he threw a can at her, striking her arm."
Paul Francis Floyd, 47, of Los Angeles, was arrested for felony child endangerment, misdemeanor battery and two counts of felony vandalism. Floyd is being held on $100,000 bail and is scheduled to appear in court this week.
Authorities said paparazzi were in the area at the time taking pictures. A secondary investigation is being conducted into a possible charge of intentional harassment of a child or ward of another person because of that person's employment.
On Thursday night King released a statement on social media saying that both she and her son were "very shaken up."
"My brave friend Judit Balogh used her self-defense training to try and keep the individual from harming James Knight while glass was shattering on him, as the perpetrator jumped on the roof until it collapsed and kicked in windows trying to get to him," King wrote. "He threw a bottle at her, hitting and assaulting her, but he couldn't catch her. Without her bravery and selflessness, I cannot imagine the outcome."
She also took the paparazzi to task for "shoving cameras in our face during the attack, whilst he was shaking and crying instead of trying to help."
King encouraged others to learn self defense.
"Mental health, drug addiction, and homelessness are issues that need to be addressed, and we desperately need more resources dedicated to helping the people suffering," she wrote. "We as a society can do better than to let those in need endanger themselves and those around them without the help they require."