Two people were killed when a Florida bus overturned after being struck by an oncoming car on the way to a high school.

Terrifying footage showed the moment of impact when a white Malibu struck the yellow school bus carrying nearly 40 people in Winter Haven, south of Orlando, early Monday morning.

'It started when this Malibu crossed over the double yellow line and hit the school bus,' Polk County Sheriff Grady Judd said at a press conference on Tuesday.

The bus was headed to Winter Haven High School when the oncoming car, driven by 23-year-old nursing student Maria Jimenez, crossed the center line and struck the side of the bus near the rear wheels, the sheriff said.

The impact ripped the tire off the bus, which then crashed head-on into an oncoming Jeep that caught fire.

'It happened in the blink of an eye. It was absolutely impossible for that driver to get any kind of control over that bus because it immediately crashed into this Jeep,' the sheriff said.

'When you look at the white Malibu, you see the black scuffs down the side of the white vehicle. That is the scuff marks from tearing the bus tire off and hitting the vehicle, and then [the bus] hit [the Jeep] head-on.' 

A passenger on the bus, 10th grader Adinaluz Prieto Oyola, 16, and the Jeep driver, DeShawn Smith, 26, were killed in the collision.

Oyola was set to attend her first cheerleading practice on the day she was killed, Polk County Superintendent Frederick Heid said at the press conference.

'Amazing young lady in every account; teachers loved her, friends loved her. Yesterday was to be her first day of cheerleading practice,' he said.

'Her cellphone is full of messages from her friend, loved ones, those checking on her initially, and those sending goodbye messages.'

A GoFundMe has been set up to support Oyola's family.

The sheriff explained that Smith was driving to work when the tragedy occurred. 

'He was on his way to work, [driving] under the speed limit, minding his own business, when all of a sudden this big yellow bus is head-on in his lane,' Judd said.

'There's absolutely nothing he could do to avoid it. It was in the blink of an eye when the crash occurred. He was simply on his way to work.'

No charges have been filed against Jimenez, who was driving to Lakeland Regional Health, where she was working, when she weaved over the center and started the deadly crash, according to the sheriff.

'She totally cooperated with us. She provided her cell phone; she interviewed with us; she gave us a voluntary blood draw. She said, "I don't remember what happened,"' Judd said.

The sheriff explained that investigators believe the stress from the crash may have affected her short-term memory. 

'She wants to be, and certainly our best wishes are, for her to be a nurse and save a lot of lives and help a lot of people. She didn't mean to create that crash. We still have an investigation to do,' he said.

Judd hailed the school bus driver, Jessica Dye, 34, a hero for her actions when the crash happened. 

'Clearly, the video evidence and all of the reconstruction that my homicide traffic team did, which is exactly perfect, shows that Jessica was not in any way at fault. She was not speeding. She was in her lane of travel, under the speed limit,' he said.

'Even though she was involved in a horrific crash, a head-on crash, and was pinned in the vehicle, she immediately rushed to the aid of the children just as soon as she could get out.'

The sheriff noted she was previously involved in another minor bus crash where she was driving and rear-ended another vehicle, and she got a traffic citation.

'One event has nothing to do with the other, but you needed to know that as well.'

Most of the 39 people aboard the bus were high school students, along with Dye and her daughter. 

At least 26 students were transported to a hospital, and at least one person was in critical condition, Judd said.