(CBS) KAUFMAN COUNTY, Texas -- Authorities in Kaufman County, in the Dallas-Fort Worth area, are looking into past criminal cases and those that were on the calendar of Chief Prosecutor Mark Hasse, who was shot dead Thursday morning in a parking lot across from the county courthouse, CBS DFW reported.
Kaufman Police Chief Chris Aulbaugh told the station that Hasse's shooting appears to have been a targeted attack and that authorities have no elevated concern for the general public.
The motive is unknown, but investigators are looking at Hasse's cases, which have included drug dealers and organized crime.
Officials confirmed that Hasse, 57, was shot in the parking lot of the department of motor vehicles. He was transported to Texas Health Presbyterian Hospital, where he was pronounced dead.
Officials said Hasse was walking to his office, from the parking lot, Thursday morning when he was assaulted by an unknown person and "shot multiple times." He was a Kaufman County District Attorney since July of 2010.
Authorities believe that at least one person -- possibly two -- were involved in the shooting. State troopers have confirmed that an all points bulletin has been put out for two males, wearing all black clothing and some type of vests, possibly tactical, CBS DFW reported.
Chief Aulbaugh said, "We had some witnesses that saw an individual fleeing the area on foot and getting into a vehicle." That vehicle is described as a possibly dark brown or silver-colored sedan, similar to a Ford Taurus, with no license plates.
"This is a horrible situation, just a tragedy," County Judge Bruce Wood told CBS News' Anna Werner. "We'd see him in the hallways every day, and he was just an outstanding person and a very well-respected prosecutor."
"This takes it to a whole new level -- your police and your front-line people is understandable, but this? This takes it to a whole new level," Judge Wood said.
Hasse's boss, Kaufman County District Attorney Mike McClellan, said Hasse has prosecuted hundreds of cases. He was asked by CBS News' Werner what hurt the most about the killing.
"That I can't get the guys who did it. Because I would really love to,'' said McClellan.
Attacks on U.S. prosecutors are rare. Contacted by CBS News, the National District Attorneys Association knew of only seven examples between 1967 and 2004.
Investigators are asking that anyone with information about the shooting, suspects or the vehicle call police. Kaufman County Crime Stoppers is offering a $10,000 reward for information leading to an arrest and conviction in the case.
A local Kaufman business is also offering $10,000 to anyone providing information in the case.
Officials from the Kaufman Police Department, Sheriff's Department and the Texas Rangers are all working the case.