What to Know
A vigil is planned for 7 p.m. Monday at the Stonewall Inn in Greenwich Village. Mourners have been gathering there to pay tribute.
Mayor Bill de Blasio placed the NYPD on "high alert" and said hundreds of counter-terrorism officers will be out in force.
Gov. Andrew Cuomo directed flags at state buildings to be flown at half-staff.
A memorial for the victims of the nation's deadliest mass shooting grew at the Stonewall Inn on Monday morning, less than a day after a spontaneous vigil drew hundreds of mourners to New York City's landmark of gay rights.
Those who turned out at the historic Greenwich Village bar on Sunday night mourned the dozens of people killed at a gay nightclub in Orlando and decried violence and intolerance aimed at the LGBT community.
"I can't even begin to comprehend it," said John Simpson, an Upper West Side resident. "It's just beyond tragic. It's just such a flood of emotions right now. Sadness. Despair. Anger and just wondering why?"
Buildings in the city's skyline also paid tribute to the victims Sunday night. The Empire State Building went dark and the One World Trade Center's spire was lit up in a rainbow. The spires of One Bryant Park and 4 Times Square were also lit up in rainbow colors.
At street level, candles, rainbow flags and bundles of flowers, some fresh, some wilted from the morning sun, had been placed in front of the Stonewall Inn, a Greenwich Village bar that became a symbol of gay rights after a 1969 police raid led to a violent street riot.
Pockets of NYPD officers, some armed with automatic weapons, stood nearby. There was a heavy police presence outside a number of gay bars and businesses throughout the night following the targeted attack in Florida.
New York City went on high alert after gunman Omar Mateen opened fire and killed at least 49 people and wounded 53 others at a gay nightclub in Orlando.
"We are in contact with law enforcement authorities in Florida, as well as the FBI, and we are closely monitoring developments in the investigation,” the New York Police Department said in a statement.
Another vigil was planned for 7 p.m. Monday outside the Stonewall Inn.
Activist Andy Humm, host of the "Gay USA" TV show, said Stonewall is "where we go when things like this happen." Sunday's gathering is spontaneous for individuals feeling a need to be together, he said.
One of those drawn to Stonewall was Jonathan Foulk, 32, of San Francisco, who left a bouquet of sunflowers on the sidewalk outside the bar.
"The thought of someone even planning something like that just breaks my heart," he said of the Orlando massacre.
Foulk, a development officer for the Trevor Project, which operates a suicide hotline to serve the LGBT community, said he worries about the impact of the shootings on gay youths.
"People will be afraid to be themselves," he said.
Mayor Bill de Blasio condemned the Orlando shootings as "not just an attack on human beings, but an attack on our values; our values of tolerance and freedom and belief and respect for all faiths."
He assured New Yorkers that there have been no credible threats made against the city, but noted that law enforcement is on high alert.
"There is no city in the world better prepared to stop terror, to stop hate crimes – you will see the evidence of that in the coming days," the mayor said.
The mayor and first lady Chirlane McCray plan to attend the vigil on Monday.
De Blasio and two police officials declined to confirm reports that Mateen was born in New York. De Blasio said there was "very limited evidence of any connection to this city." The Washington Post said his ex-wife told the newspaper his family is from Afghanistan and he was born in New York before the family later moved to Florida.
Police Chief of Department James O'Neill said there are pictures of Mateen wearing an NYPD T-shirt circulating on social media.
"At this time, he has no — absolutely no — connection to anything NYPD. I don't know where he got the shirts, but they are easily available in a lot of places throughout the United States," he said.
De Blasio said a police force of more than 500 officers specially trained to fight terrorism would be deployed, particularly at key institutions representing the gay and lesbian community, including Stonewall Inn.
New York Gov. Andrew Cuomo said in a statement he was "shocked" and "saddened" by the shooting.
"New Yorkers stand in solidarity with the people of Florida, and the LGBT community and I have directed flags at state buildings to be flown at half-staff in the memory of those who were lost in this terrible act of mass murder," Cuomo said.
“This is just one more horrific reminder of the need for Congress to pass real and sensible gun safety legislation, just as we did in New York. It is far past time for Washington to act."