Alexander was a passenger in the car someone else was driving. The driver tried to pass another car in front of them but swerved off the road to avoid a head-on collision with another car coming the other way that they didn't see.
The car with Alexander eventually hit a tree and caught fire.
High school teammate Peyton Daniels posted to social media to talk about the passing and how Alexander was the type of person who "brought joy and playfulness to everything and everyone."
Alexander committed to Pitt's football program in December as an incoming Freshman and was set to begin practising with the team later this March.
"I received a call this morning that no parent, teacher or coach ever wants to get - the news of the sudden loss of a young and promising life," said Pitt coach Pat Narduzzi in a statement. "Our entire program is shocked and deeply saddened to learn of Mason Alexander's passing."