SIMI VALLEY, Calif. — When a July Fourth fireworks display exploded and sent red and white bursts into spectators at a Southern California park, Paulina Mulkern saw shrapnel headed straight for her 4-year-old cousin.
Mulkern pushed the girl under a lawn chair and then shielded her 7-year-old cousin with her body as scorching debris flew overhead.
‘‘You feel the big old heat come right over your back,’’ she said Friday, still shaking as she recounted the explosion the night before that left her hospitalized with bruises and red marks on her back.
At least 36 people were injured as many in the crowd of thousands fled for safety. The victims, from 17 months to 78 years old, had burns and shrapnel wounds, and some were trampled, authorities and hospital officials said.
The injured included 12 children.
Police in Simi Valley, northwest of Los Angeles, said it appeared a firework exploded prematurely in its mortar, knocking over others and aiming them across the field.
Fire investigators, however, said later they had not yet determined a cause.