Dan Wheldon was killed in a horrific crash Sunday in Las Vegas.

Dan Wheldon, the winner of the 2011 Indianapolis 500, was prounounced dead on Sunday following a crash 11 laps into the IndyCar series season finale at Las Vegas Motor Speedway.

Racers did a five-lap tribute to Wheldon, and immediately the outpour of reactions - both shock and sympathy - poured in from Twitter. Here's what some people were saying about Wheldon's death:

Andretti Autosport: It is with extreme sorrow that we have lost one of our champion drivers today. Dan was an Indy 500 champion and IndyCar Series champion with Andretti Autosport-and one of our closest competitors. Dan brought such enthusiasm and passion to the sport not often seen in motorsports. We will remember Dan's tremendous racing accomplishments with our team as well his infectious personality. We would like to express our deepest sympathy to Dan's family, racing team and friends today. Dan is one of IndyCar's greatest champions.

From Twitter:

Brian Westbrook, former Philadelphia Eagles running back: Life is so short. Make the most of it & enjoy every minute you have w/ those you love. My thoughts are w/ Dan's family. RIP DanWheldon.

Hope Solo, US Women's National Team Goalkeeper: My heart hurts deeply for Dan Wheldon and his family.An amazing individual who inspired me the moment we met.RIP Dan. Your legacy lives on..

DJ Pauly D, from MTV's Jersey Shore: Sending My Thoughts And Prayers To Dan Wheldon Family And Friends We Lost A Great One Today #RIP

Barry Sanders, former NFL running back: My deepest sympathies to the IRL and friends and family of DanWheldon.

Kyle Busch, NASCAR driver: The loss of Dan Wheldon affects the whole racing community. May all our thoughts and prayers b w his family. He will b missed!

Wayne Rooney, professional soccer player: Sad news about dan wheldon. RIP. News like this puts everything into perspective. #waytoyoung

C.J. Wilson, Texas Rangers pitcher: Reading on twitter about the passing of IndyCar racer DanWheldon is extremely sobering and a reminder that life is too short already...

Kurt Warner, Super Bowl-winning former NFL quarterback: My heart & prayers go out 2 family & friends of Dan Wheldon who was killed 2day in a LV crash! That God b with u during this difficult time!

Trevor Bayne, 2011 Daytona 500 Winner: I'm sick at my stomach right now over Dan Wheldon. I just hung out w/ him a month ago and he was such an awesome guy w/ so much life in him.

Jeff Gordon, NASCAR driver: Spent a little time with Dan Wheldon several years ago in Paris for Race of Champions. Great guy, great driver. Will certainly b missed,#JG

Kevin Harvick, NASCAR driver: Terrible day for racing...RIP Dan Wheldon

Joba Chamberlain, New York Yankees pitcher: Life it to precious to take for granted. Enjoy every second u have. RIP Dan Wheldon.

Lupe Fiasco, hip-hop artist: My heart goes out the entire @indycar family and the family of DanWheldon #77 and his team. May God have mercy.