Cody Harter, 24, was driving his maroon Chevy C71 extended cab truck about 7:30 p.m. Saturday when he allegedly pulled over to a median between Interstate 470 and MO-291.
That's where he exchanged words with another driver, police said.
"It appears our victim was in traffic and involved in some type of altercation with another person in traffic," said Chris Depue, a spokesman for Lee's Summit Police Department.
Depue said many witnesses may have seen "some type of altercation" unfold between Harter and another man at the merger between the two thruways.
"Two cars are on the shoulder and [witnesses] saw two men outside those vehicles arguing in what appeared to be a disturbance or a fight," he said.
The dispute escalated and the unidentified motorist allegedly stabbed Harter before fleeing in his vehicle north on I-471, police said.
That driver is still on the lam, police said. Authorities did not say if witnesses provided descriptions of him or the vehicle he was driving.
Before the incident, Harter's family said he called them to let them know he was on his way home.
"He came down yesterday to pick up a mower," Harter's father, Mike, said Sunday. "He called his mom on the way home and said, 'I love you. I'll be home in just a bit.'"
The family made a heart wrenching plea to urge any witness who may have seen what happened to come forward to help track down the alleged killer.
"If you saw anything, even if you think it as nothing -- please call," the senior airman's mother, Kerrie, said through tears. "Let's find who did this senseless act so you're not sitting here when it's your child. Please call and send us a message ... Please."
Kerrie Harter was flanked by her husband, their daughter Kylee, his fellow Air Force reservist, Armando, and Harter's girlfriend Shelby.
In a state of devastation and disbelief, Kerrie Harter said she was still hoping this was not real.
"I keep waiting for someone to tell me it's not true," she said. "That I'm going to wake up from this. But I'm not."
She said that while son managed to survive overseas fighting and protecting the country in deployment tours to Iraq and Qatar -- and helping in hurricane relief efforts in Houston and Puerto Rico -- he somehow died on a domestic road over what cops care calling a road rage incident.
"He had been to war and back, and to die because someone was angry," she said, stopping mid-sentence. "My son drove 65 MPH because he was so frugal with his gas mileage.
"I can only imagine someone was upset because he wasn't going fast enough," she continued. "But that's not a reason to take his life and leave him there."
His sister called out the killer for ditching her brother after whatever dispute the two may have had.
"I think you're a monster," Kylee Harter said. "You not only took my brother's life but you took everything away from us."
Sitting by her and holding hands was Harter's girlfriend, Shelby.
She could barely say any words -- only that she had planned to marry Harter and felt as though she and the family "were in a dark place right now."
"He was the love of my life," she said.
Harter's mother said her son died in the arms of other good Samaritan drivers who spotted him stumbling into traffic.
"I want to thank all the people that stopped and held his hand and prayed with him," she said. "Whoever did this may have thought he died alone. He did not die alone."
Harter was in his final semester at Missouri Western State University in St. Joseph to earn a degree in engineering technology. When he wasn't racing dirt bikes he was mowing lawns for a small business he started, his family said.
"He loved his lawn care business because he could mow when he wanted to and get to the dirt track on weekends," Kerrie Harter said proudly.
And now she and the family are being forced to say goodbye.
"We're going to go home and go to the funeral home to make arrangements to bury my son," she said, breaking down in tears.
Then she recovered and said: "I don't want another mother to sit here."