Las Vegas (CNN) -- Weeks ago, Dan Wheldon was behind the wheel of a new prototype car for the IZOD IndyCar racing series -- one meant to make his sport safer, albeit ideally no less exciting.





The two-time Indianapolis 500 winner, who'd been one of a handful of key collaborators in the safety effort as identified on the racing circuit's website, never got a chance to see the refined engines at work in a real race.





Instead on Monday, his friends, colleagues and the racing world were mourning his death following a fiery 15-car wreck at the Las Vegas Indy 300.





"I lost one of my best friends, one of my greatest teammates," driver Tony Kanaan told reporters hours after Sunday's fatal crash.





"I know this is a dangerous sport. I know we're exposed to that every day, in normal life as well," he added. "But you know, you don't think about it. Today, we have to think about it."





Images from the fatal crash





Had he won Sunday's race, the Englishman with the ready smile and engaging manner would have earned a $5 million payout. Instead, he was near the back of the 34-car field when he got mixed up in a crash that featured numerous cars spinning out of control and bursting into flames, spewing smoke and debris.





"All I could see was fire and parts flying and smoke," recalled Paul Tracy, one of those involved in the crash, on Monday. "When it all came to a stop, it looked like something out of a movie set ... It didn't seem real."





An official at the Clark County Coroner's Office, who was not named per the office's policy, told CNN on Monday that Wheldon officially died from "blunt head trauma." The 33-year-old's death has been ruled an "accident."





Two other drivers seriously injured in the wreck -- J.R. Hildebrand and Pippa Mann -- were released Monday from University Medical Center in Las Vegas, IndyCar said in a release.





Mann had surgery Sunday night for a burn injury to a finger on her right hand, while Hildebrand was held overnight after suffering a severely bruised sternum. Championship contender Will Power was treated and released Sunday, IndyCar spokeswoman Amy Konrath said.





The violent crash raised fresh questions about safety, both in motor sports generally and at the Las Vegas track specifically.





Wheldon had been a driving force to address such concerns. In an early October story posted on IndyCar.com, the racing series' official website, IndyCar Vice President Will Phillips singled out the 33-year-old driver, his team and Italian manufacturer Dallara for their efforts to fine-tool a safer car model for the 2012 season.





"He's focused on what's been needed from him to provide for the feedback to Dallara and be consistent and concise," Phillips said then of Wheldon. "You couldn't have asked for more."





Wheldon was known as "a great family man"





Ironically, the new 2012 cars were expected to have components -- namely extra protection around tires -- to prevent spin-outs like the one that triggered Sunday's wreck when two vehicles' bump together, said Tracy.





"They want the cars to run a bit more in a pack, (but) these cars are not designed to bang wheels with each other at 225 mph," the veteran driver said. "Our wheels (currently) are exposed. Once you have two cars touch each other, you don't have any control."





Wheldon's death was the first for the IndyCar circuit since March 2006, when driver Paul Dana was killed in a two-car crash while warming up for the season-opening race at Homestead-Miami Speedway. It is one of several in motor sports generally, one of the most famous being the elder Dale Earnhardt's death in NASCAR's 2001 Daytona 500.





Sports Illustrated senior writer Jon Wertheim said Monday that the sheer speed of race cars, and the minimal distance separating them, means danger lurks around every turn
What day did the incident occur? What did Wheldon die of? How many Indy wins did Wheldon have before his death? What was Wheldon doing before he died? What was he testing before his death? What was the cause of death for Wheldon?
Sunday's "blunt head trauma." two-time behind the wheel of a new prototype car a new prototype car for the IZOD IndyCar fatal crash.
question: What day did the incident occur?, answer: Sunday's | question: What did Wheldon die of?, answer: "blunt head trauma." | question: How many Indy wins did Wheldon have before his death?, answer: two-time | question: What was Wheldon doing before he died?, answer: behind the wheel of a new prototype car | question: What was he testing before his death?, answer: a new prototype car for the IZOD IndyCar | question: What was the cause of death for Wheldon?, answer: fatal crash.