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A manhunt intensified Tuesday after a prominent Texas law enforcement officer was gunned down shortly after arriving for work, according to authorities.

Clinton Greenwood, an assistant chief deputy to the Harris County Precinct 3 Constable's Office, was fatally shot around 7 a.m. (8 a.m.ET) Monday morning outside a county courthouse building — "most likely just after arriving for work," Baytown Police Department Lt. Steve Dorris said at a press conference.

Police released surveillance video Tuesday afternoon of a possible suspect in the slaying, as well as footage of a dark-colored car possibly linked to the case.

They had previously released video on Monday afternoon showing a car possibly linked to the shooting. Baytown police also said they were currently looking for a white or Latin male, approximately 6 feet to 6’3’’ tall, with short hair and a medium to stocky build.

The suspect was possibly wearing a dark jacket with a patch on the sleeve and was seen in the area at the time of the shooting, police said.

Officers responding to the scene on Monday found the 30-year veteran lawman bloodied on the ground, suffering from a single gunshot wound, Dorris said. Greenwood was flown to a local hospital, where he succumbed to his injuries, he added.

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The Houston Chronicle, citing a source who asked not to be identified because of the nature of the investigation, reported on Tuesday that just four days before his murder, Greenwood told county officials he felt threatened by a man he once targeted in a corruption investigation.

Greenwood wrote an email to the county attorney's office last Thursday, according to the Houston Chronicle, saying, "I believe [this person] poses a real threat to my and my family's safety."

A possible suspect in the murder of Assistant Chief Deputy Clinton Greenwood. Baytown Police Department

Investigators told NBC News they were looking to that report and following leads in Baytown and the greater Houston area. Authorities are offering a $65,000 reward for information about the case.

Dorris had said on Monday that authorities were still investigating possible motives and any leads on the gunman.

“Whether or not he was specifically targeted, or whether this was because of the uniform he was wearing or the place he pulled up to in the morning, we just don't know that right now,” he said.

Greenwood’s nephew, Andrew Smith, said Tuesday that his uncle was a beloved figure in the community.

“He was just a great man — a good family man who loved his community,” Smith told reporters at the courthouse, near a memorial site for his uncle.

“He was loved by a lot of people,” he added.

Harris County Sheriff's Office Maj. Clint Greenwood, seen here in July 2016, was shot and killed on April 3 moments after arriving for work. Melissa Phillip / Houston Chronicle via AP, file

Brian Benken, Greenwood's former law partner, told NBC News he was "just in shock" and that the deputy constable was a fixture in the community.

"Now everybody just wants them to catch the killer," he said.

"Clint was a fixture for 30 years and not just because of his incredible personality, but because of the work he did both as a prosecutor and as a defense attorney," he added.

Harris County Chief Clerk Jill Harrison, who set up the memorial flag outside where Greenwood was killed, told NBC affiliate KPRC the shooting was “surreal.”

“It’s surreal. Clint was usually the first one here every morning, usually bringing breakfast,” she said.

"We have a job to do and we would not be doing right by Clint if we didn't get in there and do our jobs," she added.

Texas Governor Greg Abbott released a statement Monday saying his “heart goes out to the family and friends of Assistant Chief Deputy Greenwood and the Harris County law enforcement community in the wake of this heinous murder."