The victims were a 43 year old mother and her daughter, aged 12.
Heitmann was pronounced dead at the scene due to blunt force trauma and eight other people were injured. Heitmann could have exceeded 100 miles an hour before the collision, Sanchez said.
He had nearly 900,000 subscribers on YouTube and hundreds of thousands of followers on Twitter.
Heitmann, known simply as "McSkillet", rose to prominence in the online community surrounding the popular video game "Counter Strike: Global Offensive".
One other person was taken to a hospital to be treated for injuries. In December, he posted a video of the McLaren he bought, explaining that he used funds from skin trading and monetizing YouTube videos. In a YouTube video late past year, Heitmann had showcased his black McLaren 650s sports auto - the same make and model of the vehicle that caused the accident.
Reports say Heitmann was given a trade ban by the game's owner Valve earlier this year over a crack-down on gambling involving custom content, which froze him out of account and cut his income. The vehicle matches the description of the auto involved in Thursday's crash.
Aileen Pizarro worked family counselor in San Diego, and her daughter was set to begin seventh grade on Monday, the Union-Tribune reported.
Heitmann, 18, also died in the crash, which erupted into a fireball as other drivers smashed into flaming wreckage strewn across the highway lanes.
CHP officers were at the school Thursday, but officials did not say whether the two incidents were connected.