"About an hour ago, our baby was declared brain dead," the grieving father wrote Sunday. "He tried to fight so hard. He even died at one point but they brought him back. He's a little fighter. Our hearts are broken and there's a void in my soul but we will get through this … RIP Liam Mikael Kowal."

>> Click here to see the Facebook post

The fatal incident occurred Saturday afternoon in Hawthorne, California.

>> See an Instagram post about Liam here

According to the New York Daily News, Liam and his aunt were found in the street near a crosswalk after being hit by 72-year-old driver Donna Marie Higgins, Hawthorne police said.

The child was "pulseless and not breathing," while the teen suffered a leg injury, police said.

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Police said Higgins attempted to leave the scene, but witnesses followed her and kept her from fleeing.

Police said Higgins was driving under the influence, according to a field sobriety test.

Higgins was arrested and released after posting $100,000 bail. She faces charges of hit-and-run and drunken driving, both felonies.

In later updates, Kowal shared a link to a GoFundMe campaign and revealed that his son's organs would be donated.