At a campus sometimes divided by cliques and racial splits, students put aside their differences to grieve the loss of four classmates who died in a school bus crash here.

"The closest I've ever seen Lee was yesterday," Lee High School sophomore Megan Ford said. Her third cousin, Nicole Ford, was one of the four girls who died in the crash.

"It was black, white, all hugging and crying together. It didn't matter — it didn't matter at all what race we were and we were all just telling each other that we loved them and that we cared," she said.

Nicole Ford, a 19-year-old senior, and Christine Collier, 16, a sophomore, were killed at the scene of Monday's accident. A third girl, senior Tanesha Hill, 17, died later at the hospital from her injuries, and a fourth, Crystal Renee McCrary, 17, died Tuesday at Huntsville Hospital.

Four people remained in critical condition Tuesday night, including the bus driver, who was severely injured but somehow was off the bus when it plunged about 30 feet from a highway overpass.

The driver and 14 students remained hospitalized Tuesday, hospital spokeswoman Pam Sparks said.

Witnesses said a car struck the bus Monday morning on the I-565 overpass, causing it to swerve and plow into and over a concrete railing, crashing nose-first into a street below.

One witness said the car possibly blew a tire, while another said the car was speeding up and trying to get past the bus as lanes merged on the interstate ramp. The car was driven by a Lee student, Police Chief Rex Reynolds said.

Chelsea Walker, 17, who described herself as a friend of the car's driver, said she had spoken to him Tuesday morning. "He's real upset. He thinks it's his fault," she said.

Authorities have not released the name of the driver in what police said is a criminal investigation. Police spokesman Wendell Johnson said evidence will be presented to a grand jury to decide if charges such as vehicular homicide or manslaughter are warranted.

He said a criminal investigation "does not mean a crime has been committed."

Debbie Hersman, a spokeswoman for the National Transportation Safety Board, said the bus driver was found on the overpass, escaping the devastating impact that crumpled the front of the bus.

"We are trying to determine why the bus driver was on the overpass," she said at a news conference.

The bus was carrying 40 students to classes at a technical center when the accident occurred.

Lee High School, nestled deep in a quaint neighborhood of this city built on the space industry, attracts a range of students with its heavily sought college-prep courses and technical programs, such as cosmetology and car repair.