Updated

A grand jury on Wednesday declined to indict the driver of a float involved in a train collision that killed four U.S. military veterans in a West Texas parade.

Dale Andrew Hayden, the driver of the truck pulling the float, will not face charges stemming from the Nov. 15 accident that killed four veterans who had served in Iraq and Afghanistan. Sixteen other people were injured.

Midland County prosecutor Eric Kalenak had presented evidence to the 12-person grand jury.

The veterans were riding on a flatbed truck that was hit by a Union Pacific train traveling at 62 mph. The truck was the second float in a parade organized to honor wounded veterans and their wives.

The accident remains under investigation by the National Transportation Safety Board.

According to the NTSB, the railroad crossing warning system was activated 20 seconds before the accident, and the guardrail began to come down seven seconds after that. Investigators say the float began crossing the train tracks even though warning bells were sounding and the crossing lights were flashing.

Omaha, Neb.-based Union Pacific Corp. announced in December that it was adjusting the timing of the crossing signal where the collision occurred.

The veterans had been invited to Midland, a transportation and commerce hub in the West Texas oilfields, for a three-day weekend of hunting and shopping in appreciation of their service. A local charity, Show of Support, organized the trip, parade and other festivities.

Show of Support officials did not get a parade permit from the city.

In the days after the crash, Hayden was placed under a physician's care and got counseling, his attorney, Hal Brockett has said.

Hayden, who has a military career spanning more than three decades, works as a truck driver for Smith Industries, an oilfield services company. The company placed Hayden on medical leave.

Killed were Marine Chief Warrant Officer 3 Gary Stouffer, 37; Army Sgt. Maj. Lawrence Boivin, 47; Army Sgt. Joshua Michael, 34; and Army Sgt. Maj. William Lubbers, 43.