The 12-year veteran died two weeks ago after his motorcycle was hit by a car while on his way to work.
The funeral service for the 34-year-old was held at Green Hills Memorial Chapel in Rancho Palos Verdes.
"I'm going to miss you Toshio. Your contagious smile, your wonderful laughter. You gave your mind, body and soul to all of us," Chief Thomas Kang said during the funeral. "You lived one life but touched many."
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Hirai was a lead member of the Gardena SWAT team. He spoke five different languages, held a black belt in judo, had his pilot's license and grew up in Gardena. He also attended the Gardena Buddhist Church.
He leaves behind a wife and a 2-year-old son.
"He had the biggest heart," Kristen Hirai, his wife, said. "He cared so much for everybody, and he'd be really upset with me for sharing that, but he did. I think he left a little piece of himself with all of you."
The Gardena officers union set up a fund to assist the Hirai family available at this link. Checks can also be made payable to the Gardena Police Officers' Association and mailed or brought to the Gardena Police Department at 1718 W 162nd Street, Gardena CA 90247.