NEW YORK: Police officers across United States are on high alert following the murder of two police officers in New York by a deranged man on Saturday.

The gunman, 28-year-old Ismaaiyl Brinsley, had vowed in an Instagram post to put “wings on pigs” as retaliation for the slayings of black men at the hands of white police, Fox news reported on Monday.

Brinsley was black; the slain New York Police Department officers were Hispanic and Asian.

Investigators are trying to determine if Brinsley had taken part in any protests over the deaths of Michael Brown and Eric Garner, whose names he invoked in his online threat, or simply latched onto the cause for the final act in a violent rampage.

Protests erupted in recent weeks after grand juries declined to charge officers involved in Garner’s death following a New York officer’s apparent chokehold and Brown’s fatal shooting in Ferguson.

After the officers’ killings, a union-generated message at the 35,000-officer NYPD warned officers that they should respond to every radio call with two cars — “no matter what the opinion of the patrol supervisor” — and not make arrests “unless absolutely necessary”.

The president of the detectives union told members in a letter to work in threes when out on the street, wear bulletprof vests and keep aware of their surroundings.

The republicans in New York are focussing on a rift between police officers and the Mayor of New York City Bill de Blasio who recently had blamed police for using excessive force in handling the crowds.

Published in Dawn December 23th , 2014