MIDLAND -- Cheered on by a flag-waving crowd, a parade float carrying wounded veterans and their spouses was inching across a downtown railroad track when the crossing gates began to lower and a freight train that seemed to come out of nowhere bore down, its horn blaring.Some of those seated on the float jumped off moments before the train, traveling at more than 60 mph, crashed into the flatbed truck with a low whoosh and a thunderous crack.Four veterans of Iraq and Afghanistan -- including an Army sergeant who apparently saved his wife's life -- were killed Thursday afternoon, and 16 people were injured.For some of the veterans who jumped clear, training and battlefield experience kicked in, and they rushed to help the injured, applying tourniquets and putting pressure on wounds, witnesses said.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. One veteran and three spouses remained hospitalized Friday, with one spouse in critical condition.The veterans were headed to a banquet in their honor as part of a three-day weekend of dinners, deer hunting and shopping.On Friday, Mark Rosekind of the National Transportation Safety Board, standing near the intersection where the crash took place, said video might provide a fuller picture of what happened. There were cameras on the lead car of the Union Pacific train and on a sheriff's vehicle that was trailing the flatbed truck, Rosekind said.The train was moving at 62 mph, short of the 70-mph speed limit, Rosekind said. In 2006, the speed limit was raised from 40 mph to meet a growing demand for freight and to improve efficiency for passenger trains, Union Pacific spokeswoman Raquel Espinoza said.A key question for investigators is whether, after the speed limit was raised, the timing of the crossing gates was changed to give cars and trucks enough time to clear the tracks, Robert Chipkevich, who headed safety board's rail investigations unit until retiring in 2010, said in an interview.Investigators will also look at whether traffic lights in town prevented the flatbed truck in front from moving ahead, he said.The agency plans to test signals for abnormalities today, Rosekind said.Federal Railroad Administration records reviewed by The Associated Press show 10 collisions at the crossing from 1979 to 1997. Six drivers were injured. The trains involved were moving between 15 and 25 mph.No collisions have been reported in 15 years, Rosekind said."They are trained for tragedy," said Pam Shoemaker of Monroe, La., who was with her husband, a special operations veteran, on a float ahead of the one that was hit.Shoemaker said the flatbed truck she was on had just crossed the tracks and was moving slowly when she heard a train coming and looked back to see the lowered crossing gates bouncing up and down on the people seated on the float behind her.Witnesses described people screaming as the warning bells at the crossing went off and the train blasted its horn.Daniel Quinonez, who was waiting in his vehicle as the parade went by, said the float on the tracks could not go anywhere because of the one right in front of it."I just saw the people on the semi-truck's trailer panic, and many started to jump off the trailer. But it was too late for many of them," he said.Another witness, Joe Cobarobio, said that only a few seconds elapsed between when the crossing gates came down and when the train slammed into the flatbed truck with a "giant cracking sound."Joshua Michael, one of the soldiers killed, pushed his wife off the float when he saw the train coming, his wife told Cory Rogers, a friend of the couple."His first instinct was to get her out of harm's way," said Rogers, who was not at the parade.