A freight train slammed into a parade float carrying wounded veterans on Thursday in Midland, killing four people and injuring 17 others as the flatbed trailer drove through a railroad crossing on its way to a banquet, authorities said.The eastbound train was sounding its horn before it hit the float about 4:40 p.m. in Midland, Union Pacific spokesman Tom Lange said. A preliminary investigation indicates the crossing gate and lights were working, Lange said.Two people were pronounced dead at the scene, and two others died at Midland Memorial Hospital, Ryan Stout, a city of Midland spokesman, said.Seven of the injured were in critical condition, and the others were in stable condition, he said."There is going to be a very thorough investigation," Lange said. "It's obviously a very tragic incident."Photos of the float taken during the parade show about two dozen people seated in chairs set up on the back of a flatbed tractor-trailer decorated with American flags and signs identifying each veteran. A banner across the truck's front bumper reads "Heroes on Board."There were two similar flat-bed trucks carrying veterans and their spouses, police said. The first truck safely crossed the railroad tracks, but the second truck's trailer was hit by the train.Some riders on the second trailer got off before the crash.The parade was to end at a "Hunt for Heroes" banquet honoring the veterans. The wounded service members were then going to be treated to a deer-hunting trip this weekend. The events have been canceled.Lange said Union Pacific is offering help to the community and victims' families, as well as peer-to-peer counseling for the train crew, who were not injured."It's pretty traumatic for them," he said.The National Transportation Safety Board also is investigating, NTSB spokesman Peter Knudson said.Midland is about 300 miles west of Fort Worth.