Dan Wheldon was killed when his head hit a post in the fencing at Las Vegas Motor Speedway — contact that created a “non-survivable injury” to the two-time Indianapolis 500 winner.

The cause of death was revealed Thursday when IndyCar presented its findings of the Oct. 16 accident in the season finale. The crash collected 15 cars, including Wheldon, who came from behind the initial contact, launched over spinning cars and sailed about 325 feet into the catchfence.

Although the contact with the post killed Wheldon, the investigation determined several factors contributed to what became a “perfect storm.”

“The accident was significant due to the number of race cars damaged, but more importantly due to the non-survivable injuries to Dan Wheldon,” the report said. “While several factors coincided to produce a “perfect storm,” none of them can be singled out as the sole cause of the accident.

“For this reason, it is impossible to determine with certainty that the result would have been any different if one or more of the factors did not exist.”

The race had a season-high 34 cars, but IndyCar CEO Randy Bernard said Thursday the field could have had as many as 37 drivers based on the size of both the track and the pit lane. The season finale was held on Vegas’ high-banked 1.5-mile oval with multiple racing grooves, which IndyCar president Brian Barnhart said created “nearly unlimited movement on the track surface under race conditions.”

That, not the construction of the fencing, played a larger role in Wheldon’s death.

Barnhart admitted IndyCar was not prepared for the drivers to have free reign on a wide-open race track.

Most ovals have only one or two racing grooves, which the report said “restrict drivers’ naturally aggressive racing behavior (and) make the location of other competitors’ cars on the race track predictable.”