Grandma Mary Duggar’s cause of death has been revealed.

The Counting On family matriarch died of an accidental drowning in a swimming pool, Washington County Coroner Roger W. Morris confirmed to PEOPLE on Wednesday. She was 78.

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“Duggar slipped and fell into the pool and drowned,” Morris told PEOPLE on Thursday. “Her daughter Deanna discovered her body and alerted authorities, who pronounced her dead at the scene.”

On Wednesday, Radar Online reported that a 911 call was made on Sunday for a “possible drowning” at Mary’s home in Springdale, Arkansas. According to the outlet, the call came in at 4:37 p.m. and emergency assistance was requested.

“Call came in of a possible drowning at [address redacted]..that’s [address redacted]. Big house in the back … older woman, 14 echo — unconscious. Medics are responding,” the dispatcher reportedly said in the call obtained by the outlet.

News of Mary’s passing was first shared by the Duggars on their official Facebook page Sunday afternoon, where the “feisty” and “incredible” County On star was remembered by her famous family in a tribute post.

“We are so sad to share that Grandma Duggar (Mary) passed away Sunday afternoon, June 9th, 2019. Mary Lester Duggar grew up in Farmington, Arkansas and was married almost 50 years to J.L. (Jimmy Lee) Duggar who preceded her in death,” the post began. “Mary found great joy in sharing her love for Jesus and her own story of how at age 15 she asked Christ to forgive her for her sins. It was at that time she committed the rest of her life to live for Him, a commitment she kept with devotion.”

Image zoom Duggar Family/Facebook

The tribute continued on to highlight Grandma Duggar’s life successes, such as her work as a prime real estate broker and her most important role of all — being “Grandma” to her 21 grandchildren and 13 great-grandchildren.

“Grandma Mary Duggar has been on the TLC shows, 19 Kids & Counting and Counting On with her family for over 15 years. She is greatly loved and will be missed so very much! She lived a tremendous life as a follower of Christ, a wife, a devoted mother, a loving mother-in-law, and a much-loved grandmother.”

The post concluded, “We deeply appreciate your prayers for our family and all who loved Mary during this time.”

Mary’s granddaughter, Jill (Duggar) Dillard, paid tribute to her grandmother with a black and white Instagram photo and revealed the heartbreaking news. “My heart breaks,” Jill wrote. “My grandma died suddenly today! She was an amazing woman of God and such a great example to so many!”

The touching post continued, “She was a feisty, incredible woman who always took the time to talk about Jesus with everyone she knew! I know she was ready to check outta here and get her new body in heaven before the old one started giving her too much trouble! We miss you so much!!”

Following her grandmother’s death, Jana Duggar said that Mary attended church hours before she died.