Jimmie Johnson's sister-in-law speaks out after murder-suicide

Jimmie Johnson’s sister-in-law is speaking out for the first time since the harrowing news of a murder-suicide hit the airwaves.

Tragedy occurred on Monday in the Johnson family, when it was reported that the NASCAR veteran’s wife’s parents and her young nephew died in Oklahoma.

Later on Monday night, Johnson’s sister-in-law — Marianne Janway — took to Facebook to share her disbelief.

“Please tell me this isn’t really happening please god someone,” Marianne wrote on Facebook, via the New York Post.

The New York Post added that it’s unclear whether Marianne Janway is the mother of Johnson’s young nephew.

Moreover, TMZ Sports reported that police in Muskogee, Okla. are investigating the deaths as a murder-suicide. Police found the bodies of Jack and Terry Janway, along with 11-year-old Dalton Janway, at the couple’s home Monday night. They went to the house after Muskogee police received a 9-1-1 call at about 9 p.m.

Police say they discovered one body when they arrived on the scene and heard a gunshot in another area of the home. Authorities say all three individuals died as a result of gunshot wounds.

Initial reports from police allege that Terry Janway is the suspected killer. A motive as to why she killed her husband and grandson remains unknown at this time.

Johnson married Chandra Janway in 2004. The couple has two daughters, Genevieve and Lydia.

Additionally, Johnson has elected not to participate in this weekend’s Chicago Street Race following a horrific family tragedy. Legacy Motor Club released a statement on Tuesday.

“Legacy Motor Club has elected to withdraw the No. 84 Carvana Chevrolet from this weekend’s NASCAR Cup Series event in Chicago to allow Jimmie Johnson to attend to a family matter,” the statement read.

“The Johnson family has asked for privacy at this time and no further statements will be made.”

NASCAR releases statement on tragedy

The NASCAR community mourned the tragedy involving Johnson’s family this week. On Tuesday, the league released a statement.

“We are saddened by the tragic deaths of members of Chandra Johnson’s family,” the statement said. “The entire NASCAR family extends its deepest support and condolences during this difficult time to Chandra, Jimmie and the entire Johnson & Janway families.”

The Chicago Street Race is scheduled for Sunday, July 2 at 5:30 p.m. ET.

On3’s Dustin Schutte contributed to this article.