The crash happened around 4:30 Thursday afternoon.
Two flatbed trucks were hauling wounded warriors in a parade as part of the 'Show of Support - Hunt for Heroes' event held annually.
Eyewitnesses say the first truck made it across the tracks and the second trailer was about half-way across when the stop arms tried to come down on the tracks. One eyewitness said the stop arm came down, hit several people on the trailer and then came back up. The train collided with the trailer seconds later.
Other witnesses say some on the back of the trailer saw the train coming and tried to jump off or push their wives and loved ones to safety.
Sgt. Joshua Michael, 36, was one of the four killed. Michael worked as a Paramedic in Amarillo before enlisting in the military and reportedly shoved his wife to safety seconds before the train crashed.
One of the 17 injured in Thursday's crash was airlifted to UMC in Lubbock. There was no word on the patient's condition as of early Friday morning.
Investigators have yet to release any information on what may have led to the crash.
Midland County Sheriff Gary Painter told KAMC News the accident was being investigated by several agencies, including the Midland Police Department, Midland County Sheriff's Office and the Texas Department of Public Safety.
The National Transportation Safety Board is also en route and is expected to arrive in Midland sometime on Friday.
Stay with EverythingLubbock.com and watch the KAMC Morning News starting at 5:00 a.m. for more on this developing story.