Dale Earnhardt Jr.'s mother, Brenda Jackson, has died at age 65, Earnhardt's company JR Motorsports confirmed. She had been battling cancer.

"I'm glad her suffering has ended and she can be at peace," Earnhardt Jr. said in a tweet Monday. "She would be in tears of happiness over the words of support and remembrance she's been shown today. Our family appreciates it as well. She will live in our hearts forever."

CNN reported that Jackson worked at JR Motorsports as an accounting specialist since 2004. In addition to Earnhardt, the company is owned by his sister Kelley Earnhardt Miller and Rick Hendrick.

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Jackson married late NASCAR legend Dale Earnhardt in 1972, according to an obituary on JRMRacing.com. They had two children -- Kelley Earnhardt and Dale Earnhardt Jr. -- and separated in 1979. Jackson remarried in 1985 to Willie Jackson, a Norfolk, Virginia firefighter. She moved to North Carolina with her stepdaughter, Meredith, after Willie Jackson retired. She worked with her children at JR Motorsports since then.

“My mom, my biggest advocate and my friend...at peace that she’s at peace,” Kelley Earnhardt said in a tweet. “No more suffering & no more pain...made new in the arms of Jesus, reunited w/ones she loves & as a believer I’ll be reunited w/ her one day. Thank you to all that are offering your prayers, hugs & support.”

"Known for her wit, charisma and unparalleled ability to cut to the heart of any matter, Jackson became an instant favorite to her friends and colleagues at JR Motorsports when she joined the company as an accounting specialist in 2004," JR Motorsports  said in a news release. "Her sarcastic musings and straightforward approach injected a brand of humor at JR Motorsports that became part of its fabric as it grew into a full-time NASCAR racing operation in 2006 and a championship-winning organization in 2014."

NASCAR.com reported Jackson is survived by her husband, children, stepdaughter, six grandchildren and her two brothers, Robert Gee and Jimmy Gee, as well as her Pekingese dog, Scully.