Patrick Lynch, head of the Patrolmen's Benevolent Association, speaks during a news conference after the bodies of two fallen NYPD police officers were transported from Woodhull Medical Center, Saturday, Dec. 20, 2014, in New York. An armed man walked up to two New York Police Department officers sitting inside a patrol car and opened fire Saturday afternoon, killing one and critically wounding a second before running into a nearby subway station and committing suicide, police said. (AP Photo/John Minchillo)

After the murder of two NYPD police by a man with a lengthy criminal history, NYC Patrolmen’s Benevolent Association president Pat Lynch said Mayor Bill de Blasio had blood on his hands.

Previously, the union had sought to have the mayor banned from the funerals of police killed in the line of duty.

The union said the request was made because of de Blasio's "consistent refusal to show police officers the support and respect they deserve."

But there hasn't been a mayor, Republican, Democrat or Independent, in at least the recent past who hasn't been met with scorn by the powerful police union.

As former New York Times reporter David Firestone pointed out in a series of tweets:

1. A reminder that NYC's police unions have repeatedly and opportunistically abused their power and shabbily attacked every recent mayor. — David Firestone (@fstonenyc) December 22, 2014

2. In 1992, the PBA held a violent, vulgar City Hall rally against Dinkins, asking how many drug dealers he'd hugged. http://t.co/PIohwjJmuy — David Firestone (@fstonenyc) December 22, 2014

3. In 1997, police officers distributed fliers demanding that Mayor Giuliani be refused admittance to their funerals. http://t.co/L63mUjZpBd — David Firestone (@fstonenyc) December 22, 2014

4. The PBA ran ads against Bloomberg and threatened to picket the Republican National Convention in 2004. http://t.co/uRzC0VpSAh — David Firestone (@fstonenyc) December 22, 2014

5. Exploiting their huge power over public safety, NYC police unions have historically behaved less responsibly than any other public union. — David Firestone (@fstonenyc) December 22, 2014

At least the last four administrations, spanning nearly 25 years, have faced heavy criticism from the PBA.

For his part, de Blasio has asked that all protests against the killing of unarmed African-American men by police officers be suspended until after the funerals of the slain NYPD officers.

"It’s a time to step back and just focus on these families," he said. "I think it’s a time for everyone to put aside political debates, put aside protests, put aside all of the things that we will talk about in due time. In the coming days, as two families prepare for funerals and figure out how to piece their lives back together, that should be our only concern: How do we support them?"

De Blasio's police commissioner, Bill Braton said the mayor had lost the trust of "some" of his officers. Braton's comments came after NYPD officers turned their back on the mayor following a visit to Woodhull Hospital, where the two fallen cops were pronounced dead Saturday.

"I think he has lost it with some officers," Bratton said. "I was at the hospital when that event occurred.... I don't support that particular activity, I don't think it was appropriate, particularly in that setting, but it's reflective of the anger of some of them."

De Blasio angered the police union after he admitted that he had to train his bi-racial son to be extra careful during interactions with police.

"What parents have done for decades who have children of color, especially young men of color, is train them to be very careful when they have a connection with a police officer," de Blasio said. "It's different for a white child. That's just the reality in this country."