Officials said they conducted an administrative investigation of Lucas' "misconduct."
He "was terminated for his egregious violation of the City's and police department's policies," the release said.
Lucas faces a murder charge in the shooting death of 31-year-old Jonathan Price, who was fatally shot Saturday after police responded to reports of a fight at a gas station.
The Texas Rangers are investigating the shooting. In their initial release, the Rangers said Lucas' actions "were not objectionably reasonable."
The mayor and city council expressed their gratitude that community gatherings have remained peaceful and said they join the community and Price's family in mourning his death and the events of the past week, according to the release.
"We also ask that you remember our City employees, many of whom worked with both Mr. Price and Mr. Lucas as we eventually begin the work of healing our town and the community at large," the release said.
The city council had called a special meeting for Thursday night to consider the possible "discipline or dismissal" of a police officer, according to the city's agenda, but the news of his termination was posted prior to that meeting.
The special meeting begins at 6:30 p.m.
On Saturday, according to the probable cause affidavit, Price greeted Lucas when he first arrived on scene and offered his hand.
According to the affidavit, the entire interaction between Lucas and Price was recorded by a police body camera, but that video has not been released.
Lucas told the Texas Rangers he believed Price was intoxicated, according to the affidavit, and attempted to detain Price. When Price resisted, Lucas used his Taser unsuccessfully, the document said.
Price appeared to reach for the Taser, according to the affidavit, then Lucas discharged his firearm four times, striking Price in the upper torso.
Lucas' lawyer says that he was acting according to law because Price allegedly was trying to take his Taser. Price's family lawyer says that contradicts the Rangers' initial report and is asking for the release of the body cam video.