By Tom Mustin

BOULDER, Colo. (CBS4)– Investigators with the Colorado State Patrol believe the cyclist killed in a collision with a car during the Ironman Triathlon in Boulder on Sunday was at fault.

State troopers told CBS4’s Tom Mustin that it appears the rider, Michelle Walters of McCook, Neb. went outside of clearly marked lanes and swerved into the road where she was struck by a truck.

“Unfortunately, for whatever reason, the person just left the lane and jumped into the path of the truck,” said Colorado State Trooper Nate Reid. “She got ejected from the bike and was either hit or run over.”

Reid said the driver of the truck, Tim Lacey, 55, stopped. He was not speeding or drinking and most likely will not be charged in the collision.

“It was really disconcerting,” said Ellen Hart, a world-class athlete who saw Walters’ bicycle after the collision.

Walters, 34, was struck 30 miles into the 112-mile cycling portion of the race, at North Foothills Highway, or Highway 36, and just north of Broadway in Boulder at 9:54 a.m. Sunday.

She was rushed to Boulder Community Hospital but did not survive. This was her first triathlon.

(credit: CBS)

(credit: CBS)

Hart remains shaken after Walters’ death during the competition.

“All of us triathletes are heartbroken,” said Hart.

Hart is a world-class athlete who has competed in more than 100 triathlons. She came across the wreckage after Walters had been rushed to the hospital.

“There was still debris and rescue vehicles and blood on the highway,” said Hart.

Participants began with a 2.4-mile, one-loop swim in Boulder Reservoir. Athletes then continued on a challenging 112-mile, multiloop bike course, followed by a 26.2-mile running course.

There were 1,700 participants in the Ironman triathlon on Sunday.

Hart said the course was exceptionally safe, “That was a difficult intersection but it was clearly marked.”

There have been four cases of cyclists killed after incidents with vehicles in Boulder County in the past 2½ months. Reid said there is no explanation for the recent deaths but Boulder is a large county, very bike friendly with a growing number of cyclists.

“My heart breaks for people who started the day full of hope and promise and it ended up in tragedy,” said Hart.

Tom Mustin is CBS4’s Weekend Anchor. He has been with CBS4 since 2002, and is always looking for great story ideas. Connect with Tom on Facebook or follow him on Twitter @TomCBS4.