New York: New York was reeling on Sunday after the murder of two uniformed cops by a man who said he was seeking revenge for the recent killings of unarmed black men by police.
The two officers, Wenjian Liu, 32, Rafael Ramos, 40, were shot in the head through the window of their patrol car in broad daylight in Brooklyn on Saturday in an attack that shocked America's biggest city just days before Christmas.
Police named the shooter as 28-year-old Ismaaiyl Brinsley, allegedly a member of the "Black Guerrilla Family" gang. He fled to a nearby subway station after the attack, where he shot himself in the head on the platform.
The two officers "never had the opportunity to draw their weapons. They may never have actually even seen their assailant, their murderer" said New York police chief Bill Bratton.
Just hours before the shooting, Brinsley apparently boasted on Instagram of wanting to kill cops.
"They Take 1 of Ours... Let's Take 2 of Theirs," read a comment seemingly written by Brinsley next to a photo of a silver handgun, referencing the police killings of unarmed blacks.
Brinsley had been arrested numerous times previously, while living in Georgia, on charges ranging from disorderly conduct to terrorist threats, US media reported.
He also had previously been treated for mental health issues, the New York Times reported, citing court documents from Georgia that gave no further details.
By Sunday, candles and flowers had piled up at an impromptu memorial at the scene of the shooting.
The New York Jets football team held a moment of silence in honor of the police officers before their game Sunday, and one player, Nick Mangold, wore an NYPD cap as he walked into the stadium, pictures on Twitter showed.
Mayor Bill de Blasio and police chief Bratton somberly attended a mass at Saint Patrick's cathedral in New York led by Cardinal Tim Dolan.
But the double killing, in a city where murders are at their lowest rates in 20 years, further strained the already fraught relations between de Blasio and police.
A number of officers, in apparent homage to their slain colleagues, turned their backs to the mayor at the hospital Saturday night.
Police officers accuse de Blasio of failing to support them and of being too sympathetic to demonstrators who, in recent weeks, have been protesting police violence against African-Americans.
In July, Eric Garner, an unarmed father of six, died after police held him in a chokehold while he was being arrested for selling individual cigarettes illegally in New York.
Michael Brown, an 18-year-old in the Ferguson suburb of St Louis, Missouri, was shot dead by a police officer in August, sparking months of protests.
Grand jury decisions not to indict either white officer responsible triggered mass protests in New York and other US cities.
"Mayor de Blasio... the blood of these two officers is clearly on your hands," said Edward Mullins, president of the Sergeants Benevolent Association of some 11,000 active or retired New York police officers.
Earlier this month, there was even an online petition in which police asked the mayor not to attend their funerals if they died in the line of duty.
The former Republican governor of New York, George Pataki, also condemned "these barbaric acts," which he said were the "predictable outcome of divisive anti-cop rhetoric of #ericholder & #mayordeblasio #NYPD." Holder is the US attorney general.
Another police officer was killed while responding to a call in Florida, but the circumstances and motivation of that incident were still unclear.
De Blasio responded Sunday, calling it "unfortunate that in a time of great tragedy, some would resort to irresponsible, overheated rhetoric that angers and divides people."
And a number of voices called for calm and for unity, including President Barack Obama, who on Saturday "unconditionally" condemned the killing, and called on Americans "to reject violence and words that harm, and turn to words that heal."
The families of Garner and Brown also strongly urged against "any kind of violence directed toward members of law enforcement. It cannot be tolerated. We must work together to bring peace to our communities."