(CP) The three children shot and killed by a heavily-armed assailant who forced her way into The Covenant School in Nashville had spent the morning in the chapel memorising the words to "Amazing Grace," a missionary who visited the school revealed.

On Monday morning, Hallie Scruggs, 9, William Kenney, 9, and Evelyn Dieckhaus, 9, were all killed by the mass shooter, while school head Katherine Koonce, 60, substitute teacher Cynthia Peak, 61, and chef Mike Hill, 61 were also murdered.

On Facebook, missionary Britney Grayson, a pediatric doctor based in Kenya, posted a final image of the schoolchildren listening to her talk an hour before Audrey Hale, who had recently chosen to self-identify as a man, carried out the murders. Hale was shot and killed by police.

Grayson revealed that the children were learning the word "Jambo" in the chapel and were learning "all the verses of 'Amazing Grace' to sing for grandparents day next week."

"Just four hours ago, we arrived at The Covenant School in Nashville. Our dear friends invited us to speak at Chapel and stay and visit their girls' classrooms, pictured below. The kids were great. We taught them about life in Kenya, some Swahili words, and what it means to be a missionary," she wrote in the Monday post.

"We drove away at 10:12 a.m. and less than 20 minutes later, at least three children were shot right there on the campus. There are no words for this feeling. I think the normal feeling is supposed to be relief — relief that we were already gone and our lives are safe. But to do what I do makes me literally one of the most qualified people on the planet to help in that situation. Why had we driven away just minutes before? Could I have helped those children if we were still there? I feel guilty for being safe."

Grayson urged her followers to pray for those impacted, adding: "Pray for the doctors, nurses, and surgeons caring for them right now. Pray for all the little hearts that weren't physically wounded but who will never be the same. Pray. Pray. PRAY."

Nashville Police Chief John Drake said the preliminary investigation indicated the shooting was targeted. Hale, who identified as trans and previously attended the school, reportedly left a detailed manifesto and plan for the shooting at her home and in her car, a Honda Fit. Drake told NBC News he believed the attack stemmed from "resentment."

"We have a manifesto, we have some writings that we're going over that pertain to this date, the actual incident," he told reporters. "We have a map drawn out of how this was all going to take place."

Koonce was the head of the school, according to the school's website. The Nashville Presbytery confirmed to CBS News that 9-year-old Scruggs was the daughter of Chad Scruggs, the senior pastor at Covenant Presbyterian Church and former pastor at Park Cities Presbyterian Church in Dallas.

Mark Davis, senior pastor of Park Cities, told ABC News affiliate WFAA in Dallas that members of Park Cities have flown to Nashville to offer comfort to the Scruggs family, who have three other children, as they grieve.

"They are so deeply connected to this [church] body," Davis said. "Even now, members of our church are flying to Nashville to be with them. The impact they had here was enormous."

"All four of their children had that radiance; we talk about the radiance of Christ, even at a young age," he said. "They're gifted children, they really are. But they're godly children."

One parent with two children enrolled at Covenant told BBC News that Koonce was a "saint" who "did so much for those kids."

"She knew every single student by name," she added. "She did everything to help them when families couldn't afford things, it didn't matter. She found ways for them to stay."

On the school's website, Koonce wrote the school is "about more than simply educating our students," but about "helping children become who God intends them to be."

"As we capture our children's attention and their minds for learning, we also want to capture their hearts in relationships that challenge their thinking and help them learn critical skills. Our graduates attend the finest schools in the Nashville area, where they not only excel academically, but also act with character that comes from authentic faith in Jesus," she wrote.

Dieckhaus' family described the young girl as a "shining light," and said they are "completely broken" by her death. Kinney's family called him "unfailingly kind" and "always inclusive of others" as well as praising him for loving his two younger sisters.

A GoFundMe for the Kinney family states: "Will had an unflappable spirit. He was unfailingly kind, gentle when the situation called for it, quick to laugh, and always inclusive of others. He loved his sisters, adored his parents, grandparents, aunts and uncles, and was always excited to host friends of every age. Sweet Will knew no strangers, and our hearts our broken for his family as they try to find their way forward."

© The Christian Post