Family photo
MacKenzie Coyne, left, with her sister, Madison, 9, and her brother, Mason, 5. MacKenzie died Sunday, Feb. 14, 2016, from apparent complications of the flu.

PARK CITY — Just days after celebrating her eighth birthday, family friends say Mackenzie Coyne became ill and died suddenly from apparent complications of the flu.

"It's hard to believe,” said Heidi Kaiserman, Mackenzie’s second-grade teacher at Trailside Elementary School. “That's what we're all trying to do is get our head wrapped around it."

Mackenzie's classmates celebrated her birthday Friday, Feb. 12, and she went out with her family on Saturday night. After becoming suddenly ill with a stomach bug Sunday morning, family friends said MacKenzie tested positive for influenza A that afternoon. Later, she was rushed to the hospital.

"Within just a few hours they were doing CPR on her and she was gone,” Kaiserman said.

Thursday, Mackenzie's family and friends filled St. Mary's Catholic Church in Park City for her memorial service.

Kaiserman described MacKenzie as "very energetic, had the most beautiful smile."

The Summit County Health Department awaits the medical examiner's report for confirmation of the flu and whether it caused Mackenzie's death.

Statewide, the Utah Department of Health reports 226 confirmed flu-related hospitalizations this year.

Salt Lake County saw a significant increase in flu activity this past month, with two deaths reported so far this year and 117 flu-related hospitalizations, including 14 Wednesday.

Mackenzie and her family moved from Kansas City just last June. A GoFundMe account under "Mackenzie Coyne Memorial Fund" to help the family create a memorial in Park City has raised more than $28,000.

"We are prepared to be there for them and support them,” said Missy Hilton, a Coyne family friend. “I can't imagine what it would be like to have just moved to a new town where you are disconnected from all your family and all your friends."

Mackenzie's family is now headed to Kansas City for another memorial and her burial Saturday.