If the killings do turn out to have been motivated by the death of Eric Garner, they could inflame tension over race and law enforcement that have dogged New York City Mayor Bill de Blasio, sparked protests around the country and drawn in President Barack Obama and his attorney general, Eric Holder.

The officers were killed without warning and at close range as they sat in their squad car in the Bedford-Stuyvesant section of Brooklyn, Police Commissioner William Bratton told a news conference, flanked by de Blasio.
 
"Although we're still learning the details, it's clear that this was an assassination, that these officers were shot execution style," said de Blasio.

New York police have come under intense pressure in recent weeks. Protests erupted after a grand jury declined this month to charge a white police officer involved in Garner's chokehold death during an arrest attempt in July in Staten Island borough.

Bratton identified the gunman in Saturday's shooting as Ismaaiyl Brinsley, 28, and said he took a shooter's stance on the passenger side of the squad car, opening fire with a silver semi-automatic handgun. He then fled into a nearby subway station and died there from a self-inflicted gunshot wound to the head, Bratton said.

The police chief identified the slain officers as Rafael Ramos, 40, and Wenjian Liu, 32. Liu had been married for two months. Ramos had a 13-year-old son.

The killings were the first time New York City police officers have been killed by gunfire since 2011 and sparked bitter anger among some police against de Blasio, who they see as not supportive enough in the face of public anger. The mayor has had a prickly relationship with law enforcement as he tries to balance regard for civil liberties with police concerns.

Patrick Lynch, head of the Patrolmen's Benevolent Association that is the country's largest municipal police union, said, "There's blood on many hands tonight."

"Those that incited violence on the street under the guise of protest, that tried to tear down what New York City police officers did every day," Lynch told a news conference. "That blood on the hands starts on the steps of City Hall in the office of the mayor."

Demonstrations over Garner's death came on top of protests around the country over another grand jury's decision in November not to indict a white police officer who fatally shot an unarmed black teenager in Ferguson, Missouri.

Obama was briefed on the killings while on vacation in Hawaii. He later said in a statement he unconditionally condemned the shootings, adding that police officers "deserve our respect and gratitude every single day."

INSTAGRAM POSTING

An online posting suggested a link between Brinsley, who was black, and anger over the death of Garner.

Screenshots taken by various media showed an Instagram account attributed to Brinsley with a picture of a man with wire-rimmed glasses and a separate picture of a silver pistol.

The account, using the slang insult pig for police, said: "I'm Putting Wings On Pigs Today. They Take 1 Of Ours ... Let's Take 2 of Theirs."

The post included hashtags for Eric Garner and for Michael Brown, the teenager who was shot dead in August in Ferguson.

Instagram said the account attributed to Brinsley had been deleted.

Bratton was asked whether there was a link between Brinsley and the weeks of protests over law enforcement, and said this was under investigation. He added:

"There has been ... a very strong anti-police, anti-criminal justice system, anti-societal set of initiatives under way and one of the unfortunate aspects sometimes is some people get caught up in these and go in directions they should not."

He said police would investigate whether Brinsley had been part of protests in New York and in Atlanta, his last place of residence, over the Brown and Garner killings.

DIFFERENCE OVER TIMING

Brinsley had shot and seriously wounded his ex-girlfriend in Baltimore County, Maryland, early on Saturday before traveling to Brooklyn, where he had connections, Bratton said.

He said Baltimore authorities, who had responded to that shooting, warned the NYPD at 2:45 p.m. that it should be on the lookout for Brinsley. That was right around the time the shooting of the two NYPD officers took place.

But Baltimore County Police gave a slightly different timeline, raising questions about how soon in advance the NYPD was alerted.

Baltimore County Police said in a statement its investigators tracked Brinsley’s phone and determined he was in Brooklyn, and that at 2:10 p.m. they called police there to say he was in the area, warning them about the threats Brinsley had made on Instagram.

DE BLASIO AND POLICE

The Rev. Al Sharpton, a New York civil rights leader who has supported the families of Brown and Garner, said he was outraged by the officers' killings, if they were related to the men's deaths. Civil rights leaders in Los Angeles and Brown's family also condemned the shootings.

De Blasio faced a fresh tide of anger in the city, this time from some of New York's police force.

A Democrat who took office this year promising strong support for civil liberties in the city, he voiced support for protesters' rights after the Garner case and has agreed with activists that police need retraining, although he has not stepped away from New York's policy of cracking down on low-level offenses in an effort to stop more serious crimes.

The Sergeants Benevolent Association, which comprises about 12,000 retired and active New York police sergeants. "The blood of 2 executed police officers is on the hands of Mayor de Blasio," the group said in a tweet.

Police set up a perimeter for several blocks around the street corner where the shooting occurred. Only residents were allowed to cross the police line.

John Jeronimo, a 28-year-old photographer who lives in public housing nearby, predicted the neighborhood would change as more police were sent into the area.

"A lot more people are going to get checked, stopped, pulled over. From here on now it's going to be more hectic," he said.

As ambulances carrying the officers’ bodies left Woodhull Hospital in Brooklyn, police and firefighters blocked traffic along the motorcade route with squad cars and fire trucks.

Hundreds of police and firefighters stood silently at attention, saluting as the ambulances drove by on their way to the city medical examiner’s office.

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