Witnesses and parents are reportedly speaking out about the scene of a fatal school bus crash on Monday in Chattanooga, Tennessee

A “big boom.”

That’s how one witness described to local TV the sound of a bus wrapping itself around a tree on Monday in Tennessee, in a crash that killed at least five elementary school students and critically injured several more.

Another witness called it a “horror story” — and police said the resulting “complicated crime scene” in Chattanooga, Tennessee, left investigators working long into the night, examining the wreckage and trying to understand what had happened.

Three fourth-graders, a first-grader and a kindergartner were killed in the crash, Hamilton County Superintendent Kirk Kelly said Tuesday, according to the Chattanooga Times Free Press and The Tennessean. Their names have not been released.

There were 37 students on board, according to the BBC, NBC News and The Tennessean.

As parents and others arrived to the crash, they could be heard crying, according to reporter Stephanie Santostasi.

Someone screamed, “That’s my baby,” Santostasi reported.

“What has happened today is every public safety official’s absolute worst nightmare,” Chattanooga Police Chief Fred Fletcher said at a news conference. “But that is nothing in comparison to the nightmare that families and friends and our community is going through with this tragic loss to children in our community.”

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The father of some of the students on board says he has had concerns about the driver, 24-year-old Johnthony Walker, who has been charged with five counts of vehicular homicide, among other charges.

Craig Harris told Good Morning America he has previously seen Walker drive a “little faster than he probably should be going.”

“That’s the reason wphy I tried to be there in the mornings when he’s pulling up,” Harris told GMA. “And also in the evenings, because some days he would come up the street and drop them off, some days he would go down the street and drop them off, and I’m not a bus driver, so I’m not sure what their protocol is, but I kind of figured that wasn’t something he was supposed to be doing.”

Police allege that Walker was speeding and driving recklessly at the time of the crash.

Walker’s license was previously suspended for more than a year for failure to show proof of insurance, beginning in March 2014, and it was reinstated on March 28, 2015, a Tennessee Department of Safety and Homeland Security spokeswoman confirms to PEOPLE.

The Tennessee Bureau of Investigation is also conducting toxicology tests on Walker, spokeswoman Susan Niland tells PEOPLE.

Walker is being held on bond of $107,500 and his first court appearance is Nov. 29 at 8:30 a.m., a Hamilton County Courts official tells PEOPLE, adding that he has not yet entered a plea or retained an attorney.

Chattanooga Fire Department personnel work the scene of a fatal elementary school bus crash in Chattanooga, Tennessee, on Monday.
| Credit: Bruce Garner/Chattanooga Fire Department via Chattanooga Times Free Press via AP

Harris told GMA his daughter, niece and stepson were all on the bus. But they survived.

“My daughter and my stepson, they’re in a lot of pain and a little bit of shock still, but for the most part, they’re fine,” Harris said. “My niece, she’s in recovery this morning. She just got out of surgery about an hour ago, and they’re just keeping a close eye on her.”

Like other families, Harris said his world was rocked by word of the deadly crash.

“I had to sit down and really just gain my composure,” he said. “I had to calm my wife down and other family members that were also affected by this, and it’s something I never want to face again.”