Police have not released the boy's name because he is a juvenile, but his family and Vintage High School officials have identified him as Ramon Ramirez, a senior and member of the varsity soccer team.
The teen was the victim of a hit-and-run on Pear Tree Lane near Villa Lane, Napa police Sgt. Paul Paniagua said.
He was found around 11:30 p.m. Friday, and it appears his body was somehow thrown into the windshield of a parked SUV, Paniagua said. The teen might have been struck by a vehicle, Paniagua said. There are no indications that he was riding a bike or skateboard at the time of the accident, he said.
"Most of his injuries were head injuries. Another vehicle was somehow involved. We're trying to figure out how. It's still a mystery," Paniagua said.
The owner of the parked SUV was interviewed and was cleared of any involvement, Paniagua said.
Police are putting together a timeline of what happened before the incident, Paniagua said.
He said the Police Department's accident reconstruction team, school resource officers and detectives have interviewed friends of the victim.
Anyone with information on the case may text their tip to Napa Valley Crime Stoppers at 274637.