The University of Missouri (search) football player who died after collapsing at the end of a preseason workout wasn't immediately taken to the hospital across the street but instead driven to the team offices, a university police report shows.

Aaron O'Neal (search), 19, was "in full cardiac arrest" by the time campus police officer Clayton Henke and University Hospital paramedics arrived at the Tom Taylor Building on July 12, Henke wrote in a police report obtained by The Associated Press under Missouri's public records law.

"He was brought to our door in the back of a pickup from afternoon workouts," athletic trainer Greg Nagel (search) told emergency dispatchers in a 911 call from the Taylor building, according to a copy of the call obtained by the AP. "We need someone here in a hurry."

Both University Hospital and the Taylor building are across the street from Faurot Field, but on opposite sides.

Fifteen minutes after Nagel's call to 911, Henke was sent to the scene at 3:24 p.m., nearly one hour after the conclusion of the hourlong voluntary workout.

O'Neal, 6-foot-3 and 220 pounds, started to struggle during conditioning drills about 45 minutes into the session, during which players wore shorts, T-shirts and football cleats but no helmets or pads.

The backup middle linebacker slumped to the ground after the final drill and was helped off the field by a teammate.

O'Neal was unconscious when he arrived at the Taylor building, assistant athletic trainer Alfred Castillo told university police. O'Neal was taken there rather than the nearby hospital "so that O'Neal could be seen by staff members," Henke wrote.

It was not clear exactly when O'Neal fell unconscious.

O'Neal was pronounced dead at the hospital at 4:05 p.m., or just over 90 minutes after the workout ended.

The Boone County (search) medical examiner completed an autopsy the day after O'Neal's death and ruled out infection, trauma and foul play as causes of death. Complete results won't be available for several weeks.

University officials said Tuesday that they won't discuss the events leading up to O'Neal's death until after an internal review is complete.

The line between heat stroke and heat exhaustion can be difficult to define, said Douglas Kleiner, a University of Florida (search) professor of medicine and former team trainer for Auburn University (search) and the Miami Dolphins (search).

"There's a problem in sports medicine," he said. "There's not a clear-cut way of distinguishing when you get in that danger zone when it comes to heat stroke."

NCAA (search) rules require summer workouts to be supervised by strength and conditioning directors and athletic trainers. Stringent regulations governing summer workouts were put in place after the deaths of three Division I football players in the summer of 2001.

Three of Missouri's five athletic trainers were at the July 12 workout, according to a football team press release issued the next day. University officials declined to say whether any trainers left the workout early or accompanied O'Neal in the pickup that took him to the Taylor building.

O'Neal had a pulse inside the car, Castillo told police. Once inside the athletics building, O'Neal's pulse further weakened. When Castillo couldn't identify an auditory heart beat, he attached an automatic defibrillator to O'Neal in an attempt to shock him back to life, according to the report.

Paramedics arrived before Castillo could do so. They performed chest compressions in the ambulance and administered CPR en route to the hospital.

Coach Gary Pinkel (search) has said he doesn't plan to change the way summer workouts are conducted.