That's considered when the city grants permits for parades and other events, Sharp said.
"We take all steps into consideration when we permit," he said. "I hate to go down that track until all of the investigation is over, but yes we do take that stuff into account."
About 300 people attended a vigil Saturday evening in downtown Midland. They lit white candles and prayed for the victims' families and the community as a whole. The town square was lined with American flags.
Ministers prayed for residents in the town to have strength in wake of the tragedy.
"I promise you the next few days will be tough but when we get to the other side, it will be better," Mayor Wes Perry told the crowd.
"The community is grieving. We are grieving and in pain," Sharp said.
Midland resident Gery Cain said he attended the vigil to "participate in the healing that this will bring to the community."
The veterans were on their way to a banquet in their honor and were being cheered by a flag-waving crowd. It was supposed to be the start of a three-day weekend of banquets, deer hunting and shopping in appreciation of the veterans' sacrifice.
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.
Two of the injured remained in a Midland hospital Saturday night, one in critical condition and another in stable condition. None of the injuries are life-threatening, said hospital spokeswoman Marcy Madrid.
A third person was moved to another hospital, Midland city officials said late Saturday, but they did not know the hospital name or the person's condition. A fourth person, who was transferred to a Lubbock hospital shortly after the accident, had been in serious condition but it was unclear Saturday night if that remained the case.
Union Pacific spokeswoman Raquel Espinoza said the speed limit in that area was raised from 40 mph to 70 mph in 2006.
Associated Press writers Ramit Plushnick-Masti in Houston; James Beltran, Nomaan Merchant, Danny Robbins and Terry Wallace in Dallas; Angela K. Brown in Fort Worth, Texas; and Joan Lowy in Washington contributed to this report.