LAS VEGAS (AP) -- IndyCar drivers, officials and fans are mourning the death of Indianapolis 500 winner Dan Wheldon.

The 33-year-old driver was killed Sunday in a fiery 15-car pileup in a race at the Las Vegas Motor Speedway.

It happened during Lap 13 when one car swerved and another went airborne after running over the first. That set off a chain reaction involving 15 cars. Wheldon's car also flew over another vehicle and smashed into a fence on one of the track's turns. Three other drivers were injured in the crash.

Drivers were told of Wheldon's death in a meeting about two hours after the fiery, smoky crash that many drivers said was the worst they had ever seen.

There had been concerns about the high speeds at the track, where they were hitting nearly 225 mph during practice.

Three other drivers were hospitalized following the wreck. Will Power was treated and released, but Jr Hildebrand and Pippa Mann were expected to remain in the hospital overnight.

IndyCar canceled its season-ending banquet.

Indy racing fans began leaving flowers and photos at the main gate of the Indianapolis Motor Speedway to pay tribute.  The Speedway has set up a tribute to Wheldon on its homepage. To leave your condolences for his family, click here.