A 43-year-old woman and her 12-year-old daughter in the SUV were killed. They have not been identified.
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The crash caused the SUV to burst into flames, according to the San Diego medical examiner.
The deadly crash happened about 30 minutes after Heitmann crashed his sports car into the gate of Ashley Falls Elementary School, KUSI reported. After crashing through the gate, police said Heitmann got out of his car and smashed a window at the school, according to a statement released by the school.
No one at the school was hurt.
Heitmann had a popular YouTube channel where he mostly discussed video games under the name "McSkillet."
According to authorities, Heitmann was struggling with depression when he caused the crash, KGO-TV reported.