With New York City Mayor Bill de Blasio presiding at City Hall, the moment was observed at 2:47 p.m., the precise time when Officers Rafael Ramos and Wen Jian Liu were attacked in their patrol car on a street in Bedford-Stuyvesant.
"There's a lot of pain right now, we have to work our way through that pain," de Blasio said. "We have to keep working to bring police and community closer together."
Earlier Tuesday, de Blasio and his wife Chirlane made a quiet visit to the site of the shooting.
The mayor's wife placed flowers among the dozens of tributes that have been left at the scene. De Blasio stood with his head bowed.
At the request of the mayor, buildings and landmarks on New York City's skyline will dim their lights at 9 p.m. Tuesday in honor of the two officers.
The officers were killed by a man who had made threatening posts online that referred to high-profile cases of white police officers killing unarmed black men.
Also among those who've visited the makeshift memorial is Emerald Snipes. She's the daughter of Eric Garner, a black man who died after being placed in a chokehold by a white officer in New York earlier this year. His was among the deaths of unarmed black men that were referred to in threatening online posts by the man who killed the officers.
Garner's daughter left a candle at the memorial. She said she was touched by a message posted online by the young son of one of the slain officers.
Ramos and Liu were on duty in their marked patrol car around 3 p.m. Saturday in Bedford-Stuyvesant near Tompkins and Myrtle Avenues when both were shot in the head.
The gunman watched a protest over police-involved deaths earlier this month, but did not participate. Investigators said Ismaaiyl Brinsley, 28, of Georgia, was at a protest in New York's Union Square on Dec. 1, before a grand jury decided against charging a white officer in the chokehold death of Garner.
Police said Brinsley recorded part of the protest on his phone, like other bystanders. In online posts before the shooting, police say Brinsley vowed to kill police officers in retribution for the deaths of black men at the hands of white officers. Investigators are trying to determine if Brinsley latched onto the cause for the final act in a violent rampage.
On Monday, New York Gov. Andrew Cuomo, de Blasio and NYPD Commissioner William Bratton paid visits to the homes of Liu and Ramos, meeting with family members.
"The Liu family is still having a great difficulty coming to grips with this awful tragedy that has affected them, and the Ramos family, a very large family, is attempting also to deal with it," Bratton said. "We will offer them whatever help we can."
A wake for Ramos will be held Friday, from 2 p.m. to 9 p.m., at Christ Tabernacle Church on Myrtle Avenue in Glendale. A funeral service will be held at 10 a.m. Saturday at the same location before interment at Cypress Hills Cemetery. Vice President Joe Biden will attend the funeral.
Funeral plans for Liu have not yet been made public. Liu's family is traveling to the U.S. from China and will decide on arrangements after they arrive, Bratton said.
The mayor said he plans to attend services for both officers.
"It's just shock, it's unimaginable, why, these were police officers trying to help society, trying to do the right thing," Cuomo said after the meetings. "They were relatively young men just starting out their lives. Mr. Liu recently married, and gone, for no good reason, in the harshest cruelest way possible by a total coward."
A charity created after the Sept. 11 terror attacks is helping relatives of the officers by paying off their home mortgages. The Stephen Siller Tunnel to Towers Foundation announced the plan Tuesday and is seeking donations for the families.
Meanwhile, the NYPD is investigating more than a dozen threatened copycat attacks, mostly made over the Internet. In one case, an 18-year-old Brooklyn man was charged with making terrorist threats. Devon Coley surrendered to detectives in the 73rd Precinct after his Facebook postings were spotted by police. Coley reportedly admitted he was responsible for making the statements after police said he wrote the phrase "73Nextt," a reference to the 73rd Precinct in Brooklyn. He came into his precinct with his mother Sunday night and said he was remorseful for his actions.
The NYPD is also watching its vehicles for possible vandalism attempts of department equipment. They are aware of reports of lug nuts missing from parked vehicles, including one incident in the Bronx, although it is not clear if any are vandalism.
Police are on high alert, with the New York Patrolmen's Benevolent Association warning 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 bulletproof vests and be aware of their surroundings.
Borough presidents gathered at the scene of the shootings Sunday to call for peace and unity. Police officers and other mourners stood in silence Sunday during a candlelight vigil near the spot where the two officers were shot in their patrol car.
Brooklyn Borough President Eric Adams is also calling on protesters to halt demonstrations until the officers are laid to rest.
"We want to send a very clear and loud message that what happened yesterday was a strike at public safety and that which we hold dear," he said. "We are asking all New Yorkers to turn this pain into purpose...All lives matter."
Officer Wenjian Liu (left) and Officer Rafael Ramos
Members of the Ramos family spoke outside their home Sunday evening.
"I would like to thank all those who have shared their sympathy and support for our beloved family member, Rafael Ramos, who will always be loved and missed by many," the victim's aunt, Lucy Ramos, said. "I hope and pray that we can reflect on this tragic loss of lives that have occurred, so that we can move forward and find an amicable path to a peaceful coexistence. We would like to extend our condolences to the Liu family, also. Thank you."
De Blasio has ordered all flags lowered to half-staff until the officers' interments.
Liu, 32, was a seven-year veteran and married just two months ago. Ramos just turned 40 and is a two-year veteran of the force after three years as a school safety officer. Ramos was married and has a 13-year-old son.
"They were, quite simply, assassinated - targeted for their uniform, and for the responsibility they embraced," Bratton said.
Ramos was in the driver seat and Liu in the passenger seat when Brinsley walked up to the police car, took a shooting stance on the passenger side and fired his weapon several times through the front passenger window, striking both officers in the head, Bratton said.
"Officer Liu and Officer Ramos never had the opportunity to draw their weapons," he said. "They may never have actually seen their assailant, their murderer."
Brinsley fled into the Myrtle Avenue and Willoughby Street G train subway station, where he shot himself in the head. A silver semi-automatic Taurus firearm was recovered on the subway platform near his body.
Autopsy results from the Medical Examiner found that Ramos' cause of death was gunshot wounds of his head, neck and torso. Liu's cause of death was a gunshot wound of his head. Both deaths were classified as homicides.
The autopsy found that the gunman, Brinsley, died of a gunshot wound to the head and his manner of death was ruled a suicide.
Brinsley had posted an Instagram picture of a similar-looking handgun earlier Saturday, in which he said "I'm putting wings on pigs. They take one of ours, we take two of theirs...This may be my final post."
Hours before the killings, Baltimore County, Maryland police say Brinsley went to the apartment of his former girlfriend, 29-year-old Shaneka Nicole Thompson, and shot her in the abdomen. Police said he stole her phone, called her mother and said he shot her accidentally and hopes she survives. She is expected to and is talking to police.
Brinsley fled the scene before police arrived and proceeded to take a Bolt Bus to New York City. Around 1:30 p.m. detectives became aware of the Instagram posts that indicated he was in Brooklyn, and at 2:10 p.m., they made a phone call to the 70th Precinct, advising the NYPD that Brinsley's phone was pinging in their vicinity. At the same time, a wanted poster was faxed to the NYPD with information about the suspect.
Bratton said all this information came together around the same time as the suspect shot the officers. Hundreds of police officers responded to the scene, and several surrounding streets were also blocked. Many people in the neighborhood were not allowed to leave their homes.
Just prior to the shooting, police said Brinsley spoke to two bystanders on the street. He asked their gang affiliation, for them to follow him on Instagram and then said "watch what I'm about to do."
The last shooting death of an NYPD officer came in December 2011, when 22-year veteran Peter Figoski responded to a report of a break-in at a Brooklyn apartment. He was shot in the face and killed by one of the suspects hiding in a side room when officers arrived. The triggerman, Lamont Pride, was convicted of murder and sentenced in 2013 to 45 years to life in prison.
The Associated Press contributed to this story.