(CNN) -- A manhunt is under way in Texas for whoever gunned down a prosecutor outside a county courthouse east of Dallas on Thursday morning, authorities said.
Mark Hasse, an assistant district attorney in Kaufman County, was fatally shot several times as he got out of his car in the courthouse parking lot, sheriff's spokeswoman Pat Laney told CNN. Investigators are looking for an older-model, four-door sedan, either brown or silver, but it wasn't clear whether there were one or two suspects Thursday afternoon, Laney said.
"We have officers going over all of this case," she said. "Nothing has been identified yet that could have prompted this assault."
The FBI joined the search Thursday afternoon, offering assistance to the Kaufman County authorities, said Katie Chaumont, a spokeswoman for the bureau's Dallas office.
Hasse "was a very well-liked person" who had worked for the district attorney's office in Dallas County, Laney said.
The courthouse in Kaufman, about 30 miles east of Dallas, was locked down after the shooting. An e-mail circulated in the Kaufman County district attorney's office is advising prosecutors to be vigilant and careful in their own personal security, said a spokesperson for the office.
CNN's Marlena Baldacci, Nick Valencia and John Branch contributed to this report.