Click in the Eyewitness News Story Window above to watch Melissa MacBride's report from Irvine.
Police originally believed Bradshaw had an asthma attack, but an autopsy performed Thursday came back inconclusive as to a cause of death. The coroner will conduct further tissue studies and tests, which could take three to six weeks until a conclusion can be reached, Irvine police Lt. Rick Handfield said.
Students and teachers at Northwood High School are trying to cope with the loss. The school is in session Thursday, but the campus is closed to the media to allow students the chance to grieve in private.
"It's not business as usual in there. I think this is going to be a really tough day. I think it's going to be a tough few weeks," said Ian Hanigan from the Irvine Unified School District.
The young athlete collapsed shortly after 5 p.m. Wednesday at the school on the 4500 block of Portola Parkway. A school trainer immediately tried to revive Bradshaw by administering CPR.
"There was a trainer here and the trainer rendered immediate first aid and began rescue breathing. Within a few minutes, advance life support was here from the Orange County Fire Authority and they rendered advanced life support," said Lt. Handfield.
Bradshaw was in critical condition when he was taken to a local hospital. He died at the hospital around 6:30 p.m., about 90 minutes after collapsing.
Irvine police say the football team's spring practice is mostly conditioning. Players don't wear pads and helmets. Bradshaw apparently didn't suffer any kind of trauma.
Meantime, grief counselors are on hand at the campus to help students cope with the loss.
"Obviously, this is a heart-breaking day for us and the pain that we're all feeling right now is not going to go away any time soon," said Hanigan. "On behalf of Northwood High and the Irvine Unified School District, I want to extend our deepest sympathies to the family of this young man."
School officials say it is not clear whether or not the Timberwolves will have football practice Thursday, or if it will be canceled for the rest of the week.
City News Service contributed to this report.