A Tennessee school bus driver was texting at the time of a crash that killed two young girls and an aspiring teacher last year, accident investigators said Friday.

James Davenport had sent and received multiple text messages leading up to the time the two buses collided in December, Knoxville police said in a written statement. Officers have met with the victims' families to inform them of the results of the investigation.

"This has been a very difficult procedure for all involved, and hopefully, this has provided the families another step in their healing process," police said in the statement.

Police said they were informed that Davenport died this week as they were nearing the conclusion of their investigation. Knox County Sheriff's officials said he apparently died of natural causes. But an autopsy was ordered for Davenport, who had sustained serious injuries in the crash.

Deputy District Attorney Kyle Hixson said that because of Davenport's death, his office will bring no criminal case.

The two buses were traveling in opposite directions on Asheville Highway when Davenport made a sudden left turn across the concrete median and crashed into the other bus taking children home from a primary school.

Police identified the two children who were killed as Zykia Burns, 6, and Seraya Glasper, 7. The adult was 46-year-old Kimberly Riddle, a teacher's aide.

Knox County Schools Superintendent Jim McIntyre said he was outraged to learn that "the negligence, selfishness and stupidity of a school bus driver employed by one of our contractors caused the death the death of two of our precious children and one of our fine educators."

McIntyre said the deaths have spurred a review of protocols and procedures for school bus contractors in the county.

The Rev. A. Gene Thomas Jr. was Seraya Glasper's pastor.

"It's saddening and disheartening to know that he was texting while he was driving," Thomas said in a phone interview. "Unfortunately we live in a society where individuals break the law and tragically take the life of someone on else because they're negligent."

Thomas said this week's news that Davenport had died had "opened up old wounds" for Seraya's family.

"But they're strong, they've made it this far and they're going to continue to make it," he said. "We just continue to remember Seraya in a good way."

Gregory P. Isaacs, an attorney for Riddle and Glasper families, said in an email that the meeting about the law enforcement findings was "very emotional."

"In addition to the issue of distracted driving, the investigation revealed some alarming issues regarding the lack of oversight and supervision of the private school bus contractors," he said.

Isaacs said his firm plans to file a wrongful death lawsuit soon.