UPDATED | April 3, 2017 4:10 PM

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BAYTOWN, Texas (CBSDFW.COM/AP) – A deputy constable has died after he was shot moments after arriving for work at a Houston-area courthouse.

Authorities at a brief news conference did not indicate a motive for the shooting Monday morning of Harris County Precinct 3 Assistant Chief Deputy Clinton Greenwood. A manhunt is underway for the gunman.

Greenwood was airlifted to a Houston hospital where he died. He was a 30-year law enforcement veteran.

“My 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,” said Governor Greg Abbott. “Texas is taking action to strengthen penalties for those brazen enough to commit crimes against law enforcement, and we will send a message that such vile acts will not be tolerated in the Lone Star State. I am confident the perpetrator of this despicable act will be apprehended and that the murderer will be met with swift justice.”

The shooting occurred in Baytown, east of Houston. It led to the lockdown of a nearby high school and a broad response by law enforcement as authorities closed intersections as part of their search for the suspect.

Access to businesses in the area was limited as authorities conducted their search.

Later in the afternoon the Office of the Governor’s Criminal Justice Division offered an additional reward of up to $15,000 for information leading to the identification and arrest of the person or persons involved in the murder of Assistant Chief Deputy Clint Greenwood.

The award offered by the Governor’s office, combined with the Baytown Crime Stoppers award of $35,000 will bring the total amount offered to $50,000.

(© Copyright 2017 CBS Broadcasting Inc. All Rights Reserved. The Associated Press contributed to this report.)