"It's one of the most violent days we've seen in a long time. All over the city, five different police districts," Ross said. "There's no rhyme or reason. It's not like they're consolidated to one place, which is even more frustrating. It's harder to get our arms around that."
A suspect was in custody in the fatal stabbing, which police called a random, unprovoked attack. Investigators were still looking for the gunmen in the deadly shootings. Most of those killings appeared to stem from arguments that people chose to settle with guns, the commissioner said.
Authorities on Wednesday identified some of the victims, including Demetrious Pinckney, 21, brother of Dion Waiters, a Philadelphia native and Oklahoma City Thunder guard, according to sources close to the NBA player.
Pinckney, of North Philadelphia, was shot in the head on the 2300 block of Morris Street in South Philadelphia about 7:30 p.m. after some type of argument and dirt bike chase, police said. He was pronounced dead at the scene at 8:01 p.m.
Ross said police suspect, but have yet to confirm, that the dispute "had something to do with a motorcycle incident from a couple years ago. So some of these feuds will last for years and then people will choose to exact revenge in whatever way they can."
Waiters posted on his Instagram account about the death Tuesday night, showing a picture apparently of Pinckney with a dirt bike and writing that the news "crushed my heart."
Waiters will not play in Wednesday's game against the Los Angeles Clippers and was traveling to Philadelphia to be with his family.
"We were saddened to hear the news of the passing of Dion's brother, and he has our full support," Sam Presti, the team's executive vice president and general manager, said in a statement. "Dion and his family are in our thoughts and prayers during this difficult time."
A 20-year-old man also was wounded in the Morris Street shooting. He was hit in the thigh and buttocks, and was listed in critical condition at the Hospital of the University of Pennsylvania.
The first of the deadly shootings, which occurred over a three-hour period, happened at about 6:25 p.m. on the 2100 block of North Van Pelt Street in North Philadelphia.
Quadir Whitney, 21, of the city's Kingsessing section, was shot in his neck and taken to Temple University Hospital, where he was pronounced dead. A 22-year-old man was also shot and was listed in serious condition at Temple. Police said an argument apparently sparked the shooting but further details weren't available.
Shortly after 8:15 p.m., a 22-year-old man was shot dead in a drug-related killing on the 1400 block of North Vodges Street in West Philadelphia, police said.
Police said Trevor Bouknight, of West Philadelphia, was found unresponsive on a front porch there. He was pronounced dead at Penn Presbyterian Medical Center at 8:45 p.m.
At about 8:30 p.m. in North Philadelphia, 31-year-old Phillip Miller was shot in his shoulder and chest on the 2400 block of North Hollywood Street.
Miller, of North Philadelphia, was pronounced dead at Temple's hospital at 8:51 p.m. The motive for the slaying wasn't known.
The final shooting death happened on the 3100 block of West Abbottsford Avenue in East Falls, when a man was shot in his body, head and face shortly after 9:20 p.m.
The victim, who had not been identified as of Wednesday morning, was pronounced dead at the scene at 9:29 p.m. The motive for the killing remains unknown.
In the deadly stabbing, Nathan Ackison, 30, was watching his car being repaired when he was stabbed in the chest in an unprovoked attack on the 5600 block of Baltimore Avenue. He was taken to Penn Presbyterian Medical Center, where he was pronounced dead at 2:59 p.m.
Also stabbed were a 31-year-old man who had been paying his bill at the Cricket Wireless store at 5547 Baltimore Ave. and a 51-year-old man who had been sitting in his car outside the store. Both of those victims were hospitalized but survived.
A man with a knife was taken into custody near the scene.
Police on Wednesday identified that suspect as 50-year-old Ronald Stanley. Stanley was likely high on some type of drugs during the rampage and has a long criminal record, Homicide Capt. James Clark said.
Ross said the spate of violence speaks to an ongoing problem with guns on the streets, and a need for people to speak up.
"A lot of these instances, people may have heard about something brewing in the neighborhood. Don't wait," he said. "Even if you don't care about the individuals involved, think about the carnage that happens in some of these neighborhoods and how people should not be living like this. Little kids should not see this. People should have the right to have a nice quality of life."
Staff writer Chris Palmer contributed to this article.