"He immediately engaged the suspects," Ramsey said, "and there was an exchange of gunfire. . . . Officer Wilson was able to get off numerous rounds. Both suspects were, I am told, on either side of Officer Wilson firing at him at very close range, and even though he was being struck multiple times, he continued to fire until the fatal shot was fired."
Wilson's partner, Officer Damien Stevenson, was outside the store and exchanged gunfire with one of the assailants, Ramsey said.
The call of "officer down" came at 4:44 p.m.
"He was doing his duty as a police officer, trying to protect the citizens of this city," Nutter said at a news conference near Temple University Hospital, where Wilson was pronounced dead at 6:25.
One of the alleged assailants was shot in a leg and taken to Einstein Medical Center. The other, hiding his gun under his clothing, tried to blend into the crowd, but was caught at the scene, Ramsey said. Both men had been arrested previously, he said. Police did not identify the men.
Wilson was shot at least twice.
He was a volunteer in the department's body-camera program, but it was not immediately known whether he was wearing one Thursday, Ramsey said.
The commissioner met Wilson during the program's introduction in December. "He was one of the best police officers this city has to offer, period," Ramsey said.
The deadly confrontation was captured on surveillance video in the store.
Ramsey referred to recent controversies about police conduct and officer-involved shootings, and said he hoped "the same people that are talking about the issues involving police now say a prayer, and at least express condolences to his family."
Wilson had "a 9-year-old son who is now going to grow up without a father as a result of what happened here today. A 1-year-old is going to grow up without a dad because of what happened today.
"He put his life on the line to make Philadelphia a better city, a safer city," Ramsey said.
Gov. Wolf expressed his condolences in a statement, saying, "This senseless act is devastating and a stark reminder of the danger faced every day by our brave men and women in uniform."
The store is in a strip mall next to the site of Connie Mack Stadium, which was demolished in 1976. Glass from the store's front door and windows was shattered.
Robinson Rodriguez, whose family owns a grocery store at 22d Street and Lehigh, said everyone in the store ran out to the street when police cruisers started flying by. They watched as an ambulance took the officer away.
Police later came into the store, looking for witnesses, and told the Rodriguez family that the officer had died.
"I was hoping he was OK," Rodriguez said. "To hear he's dead, I don't even know what to say."
There have been robberies in the neighborhood in the past, Rodriguez said. "But nothing like this."
The last Philadelphia officer killed in the line of duty was Moses Walker Jr., who was shot Aug. 18, 2012, after his shift in an attempted robbery near a bus stop. Walker, like Wilson, was an officer in the 22d District.
"We will never stop," Nutter said, "we will never rest, we will never step back from our efforts to make sure that all of our citizens, our business owners, kids walking down the street, grandmoms going to the store, or anyone else, is safe. I ask that you keep Officer Wilson in our thoughts and our prayers, and his family."
And, Nutter concluded, "never forget him."
Recent On-Duty Deaths
Officer Moses Walker Jr.
Shot and killed Aug. 18, 2012, during an attempted robbery in North Philadelphia after completing his night shift with the department's 22d District. Walker was on his way to a bus stop in plain clothes when his assailant mistook him for a Temple University student.
Officer Brian J. Lorenzo
Killed July 8, 2012, in a crash on I-95 in Northeast Philadelphia when a drunk driver going the wrong way slammed into his motorcycle at high speed. Lorenzo was a Highway Patrol officer.
Officer John Pawlowski
Shot and killed Feb. 13, 2009, after responding to a report of a man with a weapon at Broad Street and Olney Avenue. At the scene, the man fired at Pawlowski, of the 35th District, from inside his jacket and struck him several times.
Sgt. Timothy Simpson
Killed Nov. 17, 2008, when his cruiser was struck by a speeding car driven by an intoxicated criminal fleeing police. Simpson, of the 24th District, was responding to a robbery in Port Richmond, and his death came six months after the murder of his partner, Sgt. Stephen Liczbinski.
Sgt. Patrick McDonald
Shot and killed Sept. 23, 2008, during a traffic stop in North Philadelphia when a passenger in the car, a felon who had recently been released from prison, opened fire. McDonald was assigned to the 22d District.
Officer Isabel Nazario
Killed Sept. 5, 2008, when the police cruiser she was riding in was broadsided by a man driving a stolen SUV in the city's Mantua section. Nazario was assigned to the 16th District.
Sgt. Stephen Liczbinski
Shot and killed May 3, 2008, when he confronted three robbers holding up a Bank of America branch inside a Shop-Rite in Port Richmond. Liczbinski was assigned to the 24th District.
Officer Charles Cassidy
Shot in the head Oct. 31, 2007, when he interrupted a robbery at a North Philadelphia Dunkin' Donuts store. He died the next day. Cassidy, of the 35th District, was checking the store because it had been robbed previously.
Officer Walter T. Barclay Jr.
Shot and paralyzed as a rookie officer while trying to stop a burglary at an East Oak Lane beauty shop in 1966, Barclay died from his injuries Aug. 19, 2007.
Officer Gary F. Skerski
Shot and killed May 8, 2006, while responding to an armed robbery of a bar in Frankford. Skerski was a community relations officer in the 15th District.
Inquirer staff writers Sarah Smith, Allison Steele, and Aubrey Whelan contributed to this article.