Colorado police officer fatally shot responding to assault

— -- A Colorado sheriff's deputy was shot and killed on Wednesday after responding to an assault in progress, officials said.

The officer, an Adams County sheriff’s deputy, was fatally shot in the chest after pursuing a suspect on foot in Thornton, Colorado, located about 10 miles north of Denver, police said.

"When deputies caught up to the male, the male pulled out a handgun and started to shoot at our deputies," fatally striking the officer, the Adams County sheriff's office said in a statement.

The shooter took off on foot for a second time, but was later located and taken into custody, the statement said. Police are still searching for two additional suspects in connection with the incident, who they said should be considered "potentially armed and dangerous," according to the statement.

Police told the public to seek immediate shelter and avoid the area.

Colorado Gov. John Hickenlooper confirmed the death in a statement late Wednesday, but he did not disclose the officer’s identity or the circumstances of the shooting.

“Tonight we watched as a community was on edge and a sheriff’s deputy was shot while responding to a call in Adams County,” the governor’s statement said. “We are deeply saddened to learn that the deputy has died from injuries sustained in the shooting.

“Our thoughts and prayers are with the Adams County Sheriff’s Office and the family and friends of the deputy killed,” he added.

Hickenlooper said authorities were still working to restore calm to the area as of late Wednesday evening. The investigation is ongoing.

The shooting brings the number of gun-related officer deaths in the U.S. so far this year to four, according to the National Law Enforcement Officers Memorial Fund.

On Dec. 31, 2017, a man with a history of mental health issues opened fire on deputies in Highlands Ranch, Colorado, killing 29-year-old Douglas County Sheriff Deputy Zackari Parrish. Four other law enforcement officers were wounded in the shootout. The suspect in that case was killed.

ABC News' Clayton Sandell contributed to this report.