Jimmy Carter Announces at Sunday School that His Grandson Jeremy, 28, Died of Mysterious Illness

Jimmy Carter‘s grandson, Jeremy Carter has died, PEOPLE can confirm. He was 28.

The former president announced the news while teaching a Sunday school class at Maranatha Baptist Church in Plains, Georgia, on Sunday, according to The Atlanta Journal-Constitution.

“[Carter’s] decision to come teach Sunday school is indicative of his character, how important this church is to him, teaching is to him,” the church’s Pastor, Jeremy Shoulta, told the Journal-Constitution. “The past few months have been a very emotional time for this church. There have been moments of great joy, of sadness, of grief. The church has done all it can to lift the Carters up during this difficult time.” (PEOPLE was unable to reach Shoulta for comment.)

Carter, who announced he was cancer-free during his class earlier this month (but continuing treatment), was reportedly very open about the family’s loss.

“I’m not surprised,” church member Jan Williams told the newspaper. “That’s the kind of Christian he is. Everything that happens in life, good or bad, he uses as a teaching experience. He lives his life as a lesson for other people to see.”

The politician, 91, told the church that his grandson was feeling unwell when he laid down to take a nap at his family’s Peachtree City, Georgia, home on Saturday. His mother, Annette Carter, went to check on him and found that his heart had stopped. He was taken to a hospital, where he died early Sunday, the Journal-Constitution reported. A cause of death was unclear. Fayette County coroner’s office told PEOPLE that they didn’t have information to release as of Sunday afternoon.

Shoulta told CNN that the family attempted CPR, and were “trying to keep his heart going” before he passed.

Despite the tragedy, Carter told the congregation, according to the Journal-Constitution, to “be filled with a sense of joy and thanksgiving.”

He added, “I should be joyful and thankful to God for giving me both life and freedom.”

• With reporting by ELISSA ROSEN and MARIA MERCEDES LARA