As they spend their final moments with him at Children's Hospital of Philadelphia, they are preparing to carry on his legacy through organ donation.
Elijah's mother, Sandi Shevlin, described him as golden.
"He was always so good. His laugh. His giggle. His smile. Everything about him was so pure and angelic."
His father, Michael, added, "There wasn't a bad bone in that kid's body. He loved everybody."
The Shevlins say they found Elijah face down in the water and unresponsive.
"I ran out there and I found him," recalled Michael. "I pulled him out, started CPR. My oldest son, who is almost 7 and autistic, put on his life vest and tried to save him...It was a 10-minute window that has completely broken us."
Despite lifesaving efforts, the family says Elijah has no brain activity.
"It's the worst feeling you could ever possibly imagine," Michael said.
The parents say they take extra precautions around the pool because Elijah and his brother are autistic, including installing two locks on every door.
"As a parent, you feel like you failed them, you feel like you didn't protect them, but we literally did everything, and it's such a freak accident that no parent should go through," Sandi said.
They still do not know how Elijah managed to get outside.
According to the CDC, drowning is the leading cause of death for children ages 1 to 4.
To help prevent another family from experiencing similar loss, the Shevlins are preparing to donate Elijah's organs.
"Because of how young he is, it could be mostly children he would be able to save, and it could be up to eight people," said Bill Ginley, a Gift of Life transplant coordinator,
Ginley said the region has about 4,500 people of all ages waiting for a transplant.
He said Elijah has to finish undergoing several tests.
"We would go forward and move quickly to honor Elijah and keep that legacy going for him and what his family wants him to do, and that's to live on and continue to be that bright spot for somebody."
Michael said, "If one more parent gets to have more time with their child, then maybe that was just his purpose."
Sandi added, "I truly believe this was his calling. This was what he was meant to do. He was meant to save lives. He was meant to spread goodness."
Elijah also has a twin sister and a brother. The Shevlins say they are grateful for the community's support as they navigate their grief.
A lemonade stand fundraiser is planned for Sunday at 30 Longwood Drive in Sicklerville, N.J., from 1 to 4 p.m.