CHATTANOOGA, Tenn. (CBSNewYork/CBS News/AP) — The driver of an elementary school bus that crashed in Chattanooga, Tennessee, killing at least five children, has been arrested and faces charges including vehicular homicide.

As CBS2’s Cindy Hsu reported, witnesses said the driver was speeding when he lost control and crashed into a tree. The mother of one child said she tried to warn the school about the driver’s behavior.

Calling the Monday afternoon crash “every public safety professional’s worst nightmare,” Chattanooga Police Chief Fred Fletcher told an overnight news conference that 24-year-old bus driver Johnthony Walker was charged with five counts of vehicular homicide.

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Walker was also charged with reckless driving and reckless endangerment.

According to an affidavit, witnesses told police Walker was traveling “well above the posted speed limit.”

Bond for Walker was set at $107,500. More charges against the driver could be filed.

“It’s just so sad, you know — no words, I have no words,” one mother said.

Thirty-five students from kindergarten through fifth grade were on board when the bus flipped onto its side and wrapped around a tree. Police said overnight that five children — a boy and four girls — were killed in the crash. Earlier reports put the number at six.

At a press briefing Tuesday morning, Hamilton County schools interim Superintendent Kirk Kelly said three of the students who lost their lives were in the fourth grade, one was a first-grader and the fifth was in kindergarten, CBS News reported.

“There are no words that can bring comfort to a mother or a father, and so today, a city is praying for these families,” said Chattanooga Mayor Andy Berke.

Shaken parents took their children back to school one day after the crash that also left more than 20 schoolchildren injured.

“It touched my heart because it could have been my kids,” one woman said.

Frantic friends and family members arrived at an area hospital shaking and sobbing. Jasmine Mateen lost her daughter in the crash.

“She wanted to be a doctor, and now my baby can’t be that doctor that she wanted to be,” Mateen said.

Mateen, who had two other children on the bus, said her kids told her the driver asked if they were “ready to die” shortly before the crash. She also said she repeatedly warned school officials about him.

“I’ve been calling up to the school since school started letting them know that my kids said that he’s drinking on the bus,” she said.

In the midst of the tragedy, people rallied, waiting for hours to donate blood to help those who were hospitalized.

The National Transportation Safety Board will be sending a team to Chattanooga to investigate.

“One of the first challenges is to make sure that we get all perishable evidence before it disappears. We know memories for example are very perishable. We want to get that quickly. We need to dig very deep into company operates, the driver’s history, the bus itself. We need to dig into to all of those circumstances,” said NTSB Chairman Christopher Hart.

A warrant has been issued to remove the black box from the bus and review evidence on the video camera or cameras from the vehicle, Fletcher said.

Walker is due back in court on Tuesday, Nov. 29.

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