A demonstrator is taken into custody after a citywide curfew in Baltimore, Maryland on Saturday. Thousands of people took to the streets of Baltimore as anger over the death of Freddie Gray, a young black man, turned to hopes for change following criminal charges against six police officers.

Reuters/New York

A New York City plainclothes police officer was seriously injured when he was shot in the head on Saturday while attempting to question a man from his cruiser, and authorities said a suspect was arrested and in custody.

The officer, identified by police as Brian Moore, 25, was in surgery at Jamaica Hospital Medical Center about four hours after the shooting, a hospital representative told reporters on Saturday night.

New York Mayor Bill de Blasio said Moore was "very, very seriously injured." Local media reported the officer had been shot in the face.

"It's a reminder of the dangers all of our officers face every single day," de Blasio told a news conference at the hospital. De Blasio said Moore came from a police family and has served with distinction.

The shooting comes at a time of increased national focus both on the use of force by law enforcement officers and the dangers of police work. On Friday, six officers were charged in the death of a Baltimore man who was injured while in police custody.

De Blasio's relations with New York City police fell sharply after two city officers were shot and killed in December as they sat in their patrol car, in what officials said was a targeted attack.

Hundreds of officers turned their backs when de Blasio delivered a eulogy at one of the officer's funerals, angry at what they saw as his failure to support them during a wave of anti-police protests in the city late last year.

Police arrested Demetrius Blackwell, 35, who shot at Moore and another officer at about 6.15 p.m. while they were in their car in the borough of Queens, New York Police Commissioner William Bratton told reporters.

Bratton said the officers were trying to question Blackwell, who had an extensive criminal background, after they observed him appearing to adjust an object in his waistband.

Blackwell "removed a firearm from his waistband and ... fired several times into the vehicle," Bratton said, adding "both officers were still seated in the vehicle and did not have an opportunity to get out or return fire."

Media reports said Blackwell was recently paroled after serving seven years in prison for attempted murder.