A silver Semi-automatic pistol has been recovered on a New York subway, the New York Police department said.
Police Commissioner William J. Bratton wrote in a blog that two of New York's finest were shot and killed "with no warning, no provocation".
A White House official has said that Barack Obama was briefed on the fatal shootings of two New York police officers.
The US President was informed of the shootings while playing golf in Kailua, Hawaii, where he is vacationing for two weeks with his family.
White House staff are continuing to monitor the situation, the official said.
President Barack Obama has said that he unconditionally condemned the murder of twopolice officers in New York City on Saturday, adding in a statement that police officers "deserve our respect and gratitude every single day."
The NYPD has released photographs of the two police officers who were "assassinated" by a gunman as they sat in a patrol car.
Officers Wenjian Liu,32, and Rafael Ramos, 40, were shot by 28-year-old Ismaaiyl Brinsley who then fled into a nearby underground station before killing himself.
Boxing legend and global sporting icon Muhammad Ali has been admitted to hospital with a mild case of pneumonia.
The former heavyweight boxing champion, 72, who suffers from Parkinson's Disease, is in a stable condition and has a "good prognosis", His spokesman Bob Gunnell said.
His hospital stay is expected to be a short one.
An Australian woman has been charged with murder over the deaths of seven of her children and her niece, whose bodies were found inside her home.
Mersane Warria, 37, was charged with eight counts of murder in a bedside hearing at a Queensland hospital where she is recovering from stab wounds.
The children four girls and four boys, were aged between two and 14
The 270 people who lost their lives in the Lockerbie bombing exactly 26 years ago will be remembered at a memorial service in the United States today.
Scottish law officers will be among those attending the service at the Arlington cemetery in Washington to mark the anniversary of the 1988 atrocity.
Leading the delegation will be Scotland's top prosecutor, Lord Advocate Frank Mulholland.
He has reaffirmed his belief in the guilt of the only man convicted of the bombing, Abdelbaset al-Megrahi, and vowed to track down his accomplices.
The Archbishop of Canterbury has said he is trying to bridge the split within the Anglican church over the issue of same-sex marriage.
Expanding on comments he made earlier this month, the Most Rev Justin Welby told BBC Radio 4's Desert Island Discs that he was determined to try to listen to both sides. And he admitted he has "moments" of frustration about the issue.
The Obama administration is consulting the UK, Australia and New Zealand, among other countries in hopes of organizing an international response to the cyber-attack on Sony Pictures that it has pinned onNorth Korea, a White House official told Reuters.
The US is also consulting South Korea, Japan, China and Russia for help reining in North Korea.
There is no sign at this point of any connection to the killing of two New York police officers to terrorism, police commissioner William Bratton said in a press conference.