Disney's Pop Century resort opened in late 2003.

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The 13-year-old was found in about 4 feet of water

Lifeguards were not on duty at the time

The Pop Century Resort is in Lake Buena Vista, near Orlando

CNN  — 

Two days after he was pulled from the bottom of a swimming pool at a Disney resort in Florida, a 13-year-old boy from Missouri has died.

Anthony Johnson had been playing in a pool at Disney’s Pop Century Resort on Sunday. No lifeguards were on duty at the time; signs were posted warning that swimmers swam at their own risk.

Relatives said Anthony was jumping in and out with friends when they noticed him missing, and pulled him out within minutes, according to CNN affiliate WFTV.

The boy died Tuesday morning, according to the Orange County Sheriff’s Office.

Water safety expert: ‘Drowning doesn’t just happen’

“We are saddened by Anthony Johnson’s passing and our hearts go out to his family, friends and loved ones,” a statement from Disney said. “We have reached out to his family to offer care and assistance during this difficult time.”

William Cybulski, a firefighter who was vacationing from Buffalo, New York, said he helped another vacationing firefighter and a doctor give CPR to the boy.

“You never want to see something like that, especially when you’re on vacation, or any child in general no matter where you are,” Cybulski told CNN affiliate WKMG.

Cybulski’s girlfriend, Crystal Loschiavo, told the station that she did her best to keep the family calm, and tried to soothe Johnson’s brother.

“The little boy was really upset that it was his brother,” Loschiavo said. “He kept saying ‘this is my only brother, this is my only brother. I don’t want anything to happen to him.’”

The Pop Century Resort is located in the ESPN Wide World of Sports complex in Lake Buena Vista, near Orlando.

It celebrates the “unforgettable fads of the 1950s through the 1990s” by saluting the “timeless fashions, catch phrases, toys and dances that captivated the world through the decades,” the Disney website says.

CNN’s Marylynn Ryan contributed to this report