Jinger Duggar Recalls the Moment She Found Out About Her Beloved Grandma's 'Tragic' Drowning

Nearly two years ago, the Duggars endured a heartbreaking family moment: the unexpected and tragic death of grandma Mary Duggar.

On June 9, 2019, Jim Bob Duggar's mother died after accidentally drowning in a swimming pool, Washington County Coroner Roger W. Morris previously confirmed to PEOPLE. She was 78.

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

In Jinger (Duggar) Vuolo and her husband Jeremy Vuolo's new book, The Hope We Hold: Finding Peace in the Promises of God, the Counting On couple recalls the moment they learned the family's beloved grandmother had died.

"My hand shook as I held my phone to my face. My legs had already given way beneath me, and I could feel the carpet of my friend's living room digging into my knees. I heard my mom's words, but they didn't make sense. They couldn't be true. There had to be some mistake," writes Jinger, 27, who shares daughters Felicity, 2, and 5-month-old Evangeline Jo with Jeremy.

Prior to her death, Mary had suffered "a couple [of] strokes," Jinger writes in the book, noting that she had "made a special trip to Arkansas" three months earlier so her grandmother could spend time with her daughter, Felicity.

"But she hadn't died of natural causes or passed away peacefully in her sleep. Grandma Duggar drowned in her backyard pool," Jinger continues. "The thought of my beloved grandma dying in such a tragic way made me sick. I couldn't even speak the words as Jeremy consoled me and asked what had happened."

After receiving the devastating call from mother Michelle Duggar, Jinger remembers Jeremy holding her on the couch as she "sobbed."

She recalls her husband whispering, "'Grandma Duggar loved God. She's with the Lord now. She's being ushered into glory. That's infinitely better than being here.'"

News of Mary's passing was announced by the Duggars on their official Facebook page at the time.

"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."

The tribute went on to highlight Mary's life successes, such as her work as a 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."

Jinger also posted a heartfelt tribute to Mary on Instagram, sharing a series of photos from throughout the years.

"Yesterday, this precious woman went home to be with Jesus. Our hearts are broken, yet at peace, knowing that she is now in glory with her Savior. She was the best grandma, counselor, friend, woman of faith, bargain shopping buddy, McDonald's fish sandwich lovin' lady, who was always up for an adventure — whether across town or across the world!" Jinger wrote on June 10, 2019.

"She loved the Lord more than anything, and thus shared the hope of Jesus Christ with everyone who crossed her path. She was always there for her family, and was so sacrificial in her service toward us. She will be greatly missed. Thank you for your prayers for our family during this immensely difficult time," she concluded.

The release of Jinger and Jeremy's book comes in the aftermath of her eldest brother Josh Duggar's arrest for child pornography charges. (He has pleaded not guilty, and a judge ruled on Wednesday to release him to third-party custodians as he awaits his July trial.)

After Josh was taken into custody last week, the couple spoke out, saying in a joint statement, "We are disturbed to hear of the charges against Josh. While this case must go through the legal system, we want to make it clear that we absolutely condemn any form of child abuse and fully support the authorities and judicial process in their pursuit of justice."

The Hope We Hold: Finding Peace in the Promises of God is out now.