Four employees have been fired after a 5-year-old boy died when he was left in a scorching hot van outside his day care facility in West Memphis, Arkansas, the center's parent company said Wednesday.

Christopher Gardner Jr. was found unresponsive Monday afternoon in the van outside Ascent Children's Health Services of West Memphis, where he had been left for more than eight hours on a near-90-degree day, police said.

Christopher Gardner Jr., 5, died Monday after having been left in a hot van at a day care center in West Memphis, Arkansas. Family photo / via WMC-TV

Christopher's family said he had undergone two heart operations in his young life and had been attending Ascent since he was 1 year old for help with "developmental issues." The Arkansas Department of Human Services is investigating, and police said charges are possible.

In a statement Wednesday, Dan Sullivan, chief executive of Ascent Children's Health Services, said he had personally apologized to the family and had "terminated" four of the center's employees.

"I also shared with the family that we know our staff did not follow company policies and procedures, and if they had, this tragedy would not have occurred," he said.

Sullivan said the company had offered to cover Christopher's funeral expenses. But Carrie Smith, Christopher's grandmother, told NBC affiliate WMC of Memphis, Tennessee, of which West Memphis is a suburb, that the family had declined.

"They [were] good about it," Smith said, but "justice [has] still got to be done."

"They go home to their kids," she said. "My daughter can't come home to her son, and I can't come home to my grandbaby, because he's gone."