Tayarrie Hatchett-Sims turned 15 the same day he and his grandmother, 62-year-old Bennie Harriel, died in a crash.
A GoFundMe page reports the two died as they were on their way home from Hatchett-Sims' birthday celebrations.
Those who came to pay their respects Saturday said Harriel was a nurturer and mentor for the children and adults in her Del Paso Heights community.
CHP tells FOX40 they were initially told by a witness that the Hyundai Sonata carrying Harriel, Hatchett-Sims and his friend, was stopped on the freeway with lights off when a truck towing another car plowed into it. However, investigators say they are reviewing other evidence that conflicts with that report.
Hatchett-Sims' friend was injured in the crash and was in the intensive care unit Saturday.
Two other people were injured, one of them in a subsequent crash with a truck. The truck's driver had pulled over and put on his hazard lights to help direct traffic around the fatal incident.
CHP North Sacramento is still investigating the crashes. They have not reported why the Hyundai was stopped in the roadway.