Amid heightened tensions after a fatal sniper attack on police in Dallas, Mayor Kenney on Friday called on all sides to "listen and to be willing to hear one another."
"I ask all Philadelphians not to react in hate, anger, or violence, but instead to grieve with the nation by listening to one another," Kenney said in a statement.
But area police officers reacted with outrage to the news from Dallas that five officers had been fatally shot and seven others wounded as protesters marched in response to the killings of two black men by police in Louisiana and Minnesota.
The alleged Dallas shooter had said he was upset about the recent deaths and wanted to kill white people, "especially white officers," Dallas Police Chief David Brown said.
In Folcroft, Delaware County - where two weeks ago an officer was shot seven times and survived - Sgt. Christopher Eiserman said: "It's crazy out there. There seems to be a threat everywhere you turn.
"It's like there are two sets of standards. A police officer can be killed and no one cares, but as soon as a defendant or someone else is killed, they want to have a big firestorm about it."
In Radnor Township, Delaware County, Police Superintendent William Colarulo blamed the national outrage over police-involved shootings of black men on incomplete video clips circulated by news outlets and on social media.
"One of the things I think drives this is, sometimes you have to just take a breath and let the investigation unfold and come to a conclusion," Colarulo said. "When the media puts those videos out there when the investigation is still going on, it tends to infuriate people."
Colarulo, a former chief inspector in the Philadelphia Police Department, called the Black Lives Matter movement a "violent, hateful organization that condones violence against police."
"They chant, 'Pigs in a blanket, fry them like bacon.' I give no credit to that organization. They tend to instigate rather than heal and find solutions to the problem," he said.
In response to the Dallas shootings, Philadelphia Police Commissioner Richard Ross on Friday ordered that all officers ride in pairs temporarily.
"It is very ironic that these officers were ambushed while protecting the rights of peaceful protesters. Incidents like 9/11 and many other horrific acts have forced us to alter how we do things, and now demonstrations have been added to that list."
On Friday morning, Upper Darby Police Superintendent Michael J. Chitwood sent his 133 officers a note titled "Safety."
"While the overwhelming majority of our community and our country support our efforts," he wrote, "there is a very small segment of extremists who wish to do us harm.
"I implore each of you to continue to be vigilant in the performance of your duties," he continued. ". . .Your lives matter."
"The officers [in Dallas on Thursday night] were doing what they are paid to do - protecting people, people who were peacefully protesting, and they were assassinated. That's unconscionable, unacceptable, and unreal. When you look at that, you see how policing in America has changed."
Patrick Colligan, president of the New Jersey State Policemen's Benevolent Association, issued a statement Friday saying that the Dallas attack "comes on the heels of yet another viral video of a police shooting."
John McNesby, president of Fraternal Order of Police Lodge 5, said he was on the phone with Philadelphia police officials as early as 5:30 a.m. Friday to discuss any changes that might be made to protect officers.
"It's tragic," McNesby said of the Dallas shootings. "When an officer goes down, whether it's in Philadelphia or anywhere, it hits us all."
McNesby said the Philadelphia officers are shaken. "There's a sense of anger; there's a sense of caution," he said. "There's a little bit of everything."
With large protests expected in the city during the Democratic National Convention this month, officials said they would remain vigilant. Federal, state, and local law enforcement have spent 10 months fine-tuning the security plan for the event to address possible scenarios, Secret Service spokesman Robert Hoback said.
A Philadelphia police officer, who asked that his name not be used because he did not have official permission to speak, said he was at a loss for words after the events in Dallas.
"I was raised to look at police officers as people who help you, and now we're seen as enemies in some quarters," he said. "It's hard to reconcile."
The 21-year department veteran said that people are starting to regard police officers as all being part of one national department instead of individual departments.
"It's hard to explain that an action that's taken 1,800 miles away from you can somehow now make you a target."
Staff writers Stephanie Farr, Caitlin McCabe, Chris Palmer, Michael Boren, and Jeremy Roebuck contributed to this article.