Texas Prosecutor's Slaying Rattles Colleagues Mark Hasse was a top-notch prosecutor in northeast Texas with a "passion for putting away bad guys" and never shied from taking on cases involving dangerous people or organizations, his former colleagues say. Now investigators are sifting through Hasse's case files seeking clues to why he might have been targeted, after a masked gunman fatally shot the assistant district attorney Thursday morning in a brazen attack outside his office in the Kaufman County Courthouse. The slaying rattled fellow prosecutors across the state and angered those who worked with him in Kaufman, located about 33 miles southeast of Dallas. "I hope the people that did this are watching, because we're very confident that we're going to pull you out of whatever hole you're in," Kaufman County District Attorney Mike McLelland said Thursday during a news conference. We're going to bring you back and let the people of Kaufman County prosecute you to the fullest extent of the law. McLelland said Hasse, 57, understood and accepted the dangers of his job. "You know there is the potential for somebody bad to do something to you, because they've done something bad to somebody else," McLelland said. But, he added, Hasse "had an absolute passion for putting away bad guys. He enjoyed nothing better. Just before 9 a.m. Thursday, a masked gunman shot Hasse multiple times in the parking lot behind the Kaufman County Courthouse annex, county authorities said. Hasse was taken away in an ambulance, but it's unclear whether he died at a hospital or en route. This undated handout photo provided by the Kaufman County Sheriff's office shows assistant district attorney Mark Hasse, 57, who was shot and killed Thursday morning, Jan. 31, 2013, in Kaufman, Texas. Authorities said they were searching for two suspects that attacked him as he exited his vehicle in the parking lot behind the Kaufman County Courthouse annex where he worked. (AP Photo/Kaufman County Sheriff) Close Police did not immediately indicate a motive in the slaying, an no arrests had been made as of early Friday morning. A $20,000 reward was being offered in the case. Doug Lowe, longtime district attorney in nearby Anderson County, said Hasse's death is disturbing for all who prosecute crimes in Texas. "We are a tight group of people, and my heart bleeds for his family and his office," Lowe said. This reminds us all that we deal with some very, very bad people. Lowe said he keeps a pistol in his office but plans to start taking it with him. "This is pretty scary," he said. I may be packing heat for a while. Wayne Gent said he had a security system installed at the courthouse when he served as Kaufman County judge, but that no system could prevent an outdoor shooting. "It's going to take a long time to get over this," said Gent, an attorney whose law office is on the courthouse square. And the thing is - everybody's vulnerable. The Kaufman County DA's office was to remain closed Friday. McLelland said his office, the county and state had suffered a "devastating loss" and called Hasse a spectacular prosecutor. Hasse, who had been chief of the organized crime unit when he was assistant prosecutor in Dallas County in the 1980s, had worked in Kaufman County for three years. McLelland said Hasse worked hard and was the office "storyteller." Hasse also was a pilot, but he suffered life-threatening injuries in a 1995 crash when he was flying a World War II-vintage plane, McLelland said. He also had been president of the Dallas chapter of Mothers Against Drunk Driving. Suzette Pylant, a victim advocate for MADD North Texas, was working with Hasse on a drunken driving case at the time of his death, The Dallas Morning News reported. She last met with him on Dec. 21. "He was one of those guys who was always going to wear the white hat," she told the newspaper. Associated Press writer Angela K. Brown in Fort Worth contributed to this report.