“About a few hundred” current and retired police officers were behind the anti-Bill de Blasio banner that flew over the Hudson River in New York on Friday, ex-cop and blogger John Cardillo told the New York Daily News. But the group is choosing to remain anonymous for now, because they’re unsure how their unions will react to the incident.

“De Blasio, Our Backs Have Turned to You,” read the banner attached to a plane that circled the city Friday morning, a reference to when police officers turned their backs on the New York City mayor when he delivered a statement at a Brooklyn hospital following the fatal shootings of two police officers last week. Ismaaiyl Brinsley, the Maryland man who committed the shootings, said he did so in retaliation for the police-involved deaths of Mike Brown in Ferguson, Missouri, and Eric Garner, in Staten Island, New York. Grand juries in both cases didn’t indict the officers, which led to protests across the country.

Tensions between de Blasio and the NYPD have been running high amid the Garner decision and the killings of Officers Wenjian Liu, 32, and Rafael Ramos, 40. The mayor spoke about advising his half-black son, Dante, to be extra cautious when dealing with the police, which angered officers.

“We had a bad relationship with [former Mayor David] Dinkins, but Dinkins never came out and said he worried about his son’s safety with the NYPD,” Cardillo told the Daily News about what cops have been saying to him. Dinkins was the city’s first and only black mayor in the early 1990s. “They said that was just beyond the pale. They felt that if he hadn’t said that, tensions would not have been inflamed.”

Cardillo said that the anti-de Blasio ad cost $1,200 and that it was paid for by “about a few hundred cops,” both current and retired. On his blog, Cardillo released a statement he said came from a coalition of current and retired officers that blasted the mayor.

“It is our opinion that Mayor de Blasio's dangerous and irresponsible comments about his and his wife's concern for their son's safety at the hands of the NYPD fueled the flames that led to civil unrest, and potentially to the deaths of PO Wenjian Liu and PO Rafael Ramos, as well as the continued threats against NYPD personnel,” the statement said. “The mayor shows us no respect, and encourages the public to follow his lead.”

Individual members don’t want to be identified yet because “they’re waiting to see where their unions fall on this,” Cardillo told the Daily News.

De Blasio has asked protesters in support of Brown and Garner to stop demonstrating until the slain officers were buried. Ramos’ wake was held Friday, and his funeral was scheduled for Saturday. Vice President Joe Biden is expected to attend the funeral, according to USA Today. Meanwhile, JetBlue has offered to fly law enforcement officers around the country to the funeral for free. As of Friday afternoon, about 700 officers have taken up the airline’s offer, according to breaking news Twitter feed PzFeed.

At Ramos’ wake, the officer was remembered for his faith and professionalism.

“He was very even-keeled,” Capt. Sergio Centa, Ramos’ commander, told the New York Times. “Nobody deserves to die the way he died, especially a police officer.”

The Rev. Ralph Castillo, pastor at the Christ Tabernacle Church in Queens, where the wake was held, told the Times that Ramos had an “infectious smile.” Ramos was an usher at the megachurch.

“When I think of Ralph I think of his smile and his consistency,” he said. “He didn’t have to be there. This is something he chose to do. He was faithful and consistent.”  

Funeral arrangements for Liu have yet to be scheduled because the family is waiting for relatives from China to arrive in the United States, according to the Times.