As a licensed peace officer in Texas, Hasse could openly carry a firearm and make arrests. According to the Texas Commission on Law Enforcement Officer Standards and Education, Hasse obtained his license in 1988 and kept it current through 1995. He then allowed it to lapse for 16 years before renewing it in July 2011.
"If you saw Mark around the office or the courthouse, he generally had a pistol," said Bill Wirskye, a Dallas attorney who recently served as a special prosecutor on a murder case in Kaufman County.
Wirskye, a former Dallas County prosecutor, said prosecutors in Texas have been known to carry guns, although it's not typical.
"I don't think (Hasse) lived in fear, but he was always careful," Wirskye said. "He knew the job carried certain dangers."
Along with looking at Hasse's cases, authorities are monitoring video surveillance cameras from convenience stores and other businesses in the area to see if a vehicle linked to the killing was spotted. The vehicle is believed to be an older model, gray, four-door sedan.
Authorities also hope that a growing pot of reward money will lead to an arrest. By late Friday, more than $70,000 had been put up, with $30,000 coming from Dallas County DA Craig Watkins' asset forfeiture fund.
"We will follow every lead that we receive," Aulbaugh said.
The Kaufman County Courthouse reopened Friday, and many county employees were back at work, although the DA's office remained closed.
"We're in mourning," County Judge Bruce Wood said during an interview in his office. "I think we're still in a state of, 'We can't believe this happened.'"
Robbins reported from Dallas.