NASCAR Legend Jimmie Johnson on 'Brink of Retirement' as He Helps Family Cope With Tragedy After Murder-Suicide: Sources

NASCAR legend Jimmie Johnson is considering hanging up his racing gear for good as he helps his family cope with an unimaginable tragedy, RadarOnline.com has exclusively learned.

Insiders close to the Johnson brood claim that Jimmie is "on the brink of retirement" in the wake of a murder-suicide that police believe was the result of his mother-in-law, Terry Janway, shooting her husband, Jack, and grandson Dalton before turning the gun on herself.

Jimmie's wife, Chandra Janway, is now reeling from the horrific loss of her parents and 11-year-old nephew while grappling with the circumstances after the disturbing events that took place on June 26.

Muskogee police officer Lynn Hamlin told PEOPLE the department got a 911 call from a woman believed to be Terry that fateful night "who stated that there was a disturbance and someone had a gun" before quickly hanging up.

When cops arrived at the family's Oklahoma residence, Jack was found dead in the hallway near the front door before they heard a single gunshot farther inside the home.

Other officers rushed to the scene and discovered the bodies of Terry and Dalton.

Pals believe the tragedy be the end of the road for Jimmie's racing career after he pulled out of a race just days after the shocking incident.

"This is just an unspeakable event that Jimmie, his wife, Chandra, and their two children are trying to process," a family friend shared amid the ongoing investigation. "You never expect this kind of horror to land on your own doorstep."

"This is a life-changing event in the worst possible way, and I know Jimmie's focus is all about helping Chandra and his kids through this," the insider said. "Racing is the furthest thing from his mind. He wants to be home trying to heal his family's wounds now that they need him more than ever."

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Those in the NASCAR community have also been rocked by the devastating tragedy and the potential that Jimmie may understandably put racing on the backburner. "Jimmie is not only on the Mount Rushmore of NASCAR drivers, he's a friendly guy with a great sense of humor. All of NASCAR is mourning his losses," one source said.

RadarOnline.com has reached out to Jimmie Johnson representatives for comment.