Transcript for New Details on High School Football Injury
A California high school football player in medically induced coma after a hard hit to the head. ABC's Matt Gutman has that story for us. Reporter: It seemed like a routine tackle. He's down and he looks like he's in pain. Reporter: But number 18 is slow to get up. He seems to try to shake it off then wobbles to the surveillance. The 17-year-old varsity staple propped up by a teammate helping him to the bench. Came off the field, everything seemed Normal. He went through like concussion symptoms. Reporter: The concussion so severe he collapses flopping under that bench. Rushed to the hospital for emergency surgery to stop the bleeding, swelling and pressure on his brain. He had what was supposed to be an added security measure against concussions. Reidel's inside impact helmet rimmed with sensors that alert coaches to hits that could cause brain injuries. That sensor is in there to kind of monitor the severity of certain impacts and frequency of certain impacts as well. Reporter: A product similar to this called brain sentry. A red light will blink if a player sustains a hard hit. If a coach sees a red light like this he at least knows to take a second look at a player wearing this helmet. In his case the school district says his helmet sensor did not go off. Riddell saying "We are hopeful he has a full recover" since few facts are known it would be inappropriate for us to speculate on the circumstances surrounding the incident." Nava remains in an indunesed coma but overnight his brother posting good news on Facebook. He is breathing on his own. For "Good morning America," Matt Gutman, ABC news, Los Angeles.
This transcript has been automatically generated and may not be 100% accurate.