Manhunt intensifies for gunman in ambush killing of Texas deputy constable

— -- A manhunt is intensifying in Texas for the gunman who allegedly shot and killed a veteran deputy constable in an ambush at a courthouse, a federal source told ABC News.

Asst. Chief Deputy Clint Greenwood of the Harris County Precinct 3 Constable’s Office, a 30-year veteran, was shot Monday around 7 a.m. local time as he was arriving for work at the courthouse in Baytown, Texas, about 30 miles east of Houston, Baytown Police Department Lt. Steve Dorris said at a news conference Monday.

Responding officers rendered aid but Greenwood later died at the hospital, officials said.

No suspects have been named but Baytown police Monday night released a video clip of a car potentially belonging to the suspect.

Baytown police said they are looking for a "white or Hispanic male, approximately 6’0 to 6’3 tall, short hair and medium to stocky build." They say the suspect may have been "wearing a dark jacket with some type of patch on the sleeve and was seen in the area around the time of the shooting."

Greenwood, who was married, had a career in Harris County for nearly 30 years. Beginning in 1988 he worked at the Harris County District Attorney’s Office and he later worked at the Harris County Precinct 4 Constable’s Office and the Harris County Sheriff’s Office. In January, he was selected to serve as Assistant Chief in the Harris County Precinct 3 Constable’s Office, officials said.

“Thousands of men and women faithfully wear the badge of a Texas peace officer day in and day out in Houston and Harris County. ... They answer a high call to service for their fellow man," said Harris County Sheriff Ed Gonzalez. "That was the call that Assistant Chief Clint Greenwood answered over decades of service. His bravery and sacrifice will not be forgotten and will not go unanswered.”

The Office of the Governor’s Criminal Justice Division is offering a reward of up to $15,000 for information leading to the arrest of the suspect or suspects. Baytown Crime Stoppers has also offered a reward of $35,000.

Tips can be submitted at the Baytown Crime Stoppers hotline at 281-422-TIPS or the Texas Crime Stoppers hotline at 1-800-252-TIPS.