On TV, the images stood out amid the usual Mardi Gras sights of grand floats, flying beads and shouting people jammed behind barricades.

A pair of black shoes, a few feet apart and pointing in different directions, in the middle of the street.

Yellow tape fluttering in the breeze.

Band instruments, unattended, lying on the ground.

Children, so still, on stretchers.

A dozen members of the Gulf Shores High School Marching Band were injured at the start of that city’s Mardi Gras parade Tuesday morning when an SUV struck them from behind. Authorities said a 73-year-old man from Fairhope was driving and there was no intent to harm, but beyond that little was known by late afternoon about what happened and why.

Six high school students and six middle school students were injured. Three were in critical but stable condition Tuesday afternoon. Most were taken to South Baldwin Regional Medical Center, some to Pensacola and one to USA Medical Center in Mobile.

At an afternoon news conference, Gulf Shores city spokesman Grant Brown said the SUV was part of an American Legion unit lined up behind the band. As the parade was about to begin on Highway 59, the SUV “accelerated and struck them from behind,” he said.

The driver cooperated with police, voluntarily giving blood samples. He had not been charged as of Tuesday afternoon and police were not releasing his name. Gulf Shores Police Chief Ed Delmore did say that there were no drugs or alcohol involved.

“We are certain at this point that it was not an intentional act. It was an accident.”

However, Delmore could not say whether the driver was at fault or whether a mechanical failure occurred.

Some of the children were trapped under the vehicle. Because so many first responders were already at or in the parade, they converged on the scene immediately to begin triage and prepare the children for transport to hospitals. Those injured were between the ages of 12 and 17.

Counseling for the uninjured band members was made available at the high school, and would be available Wednesday for all students, Superintendent Eddie Tyler said. Tyler, a former principal of Gulf Shores High School, said the band members were released to their parents and those of driving age were not allowed to drive themselves home.

The Gulf Shores parade was called off, but the afternoon parade in Orange Beach went on as scheduled. Orange Beach Mayor Tony Kennon said on Facebook that he asked Gulf Shores Mayor Robert Craft for his O.K. before deciding to go ahead.

Police officers from Gulf Shores and Orange Beach carried the banner of the marching band in the Orange Beach parade.

“The biggest message I would send to parents is, my gosh, hug your kids tonight,” Brown said.