"The department's in mourning," Ramsey told reporters about an hour later after 14 motorcyle officers escorted an ambulance bearing Walker's body to the morgue. "This has been a terrible year."
Ramsey said Walker was a "mellow" man who was always smiling. "He was known as a gentle individual," he said. "He wouldn't harm a fly."
Walker was not married and had no children. He is survived by his mother and five siblings.
He was a deacon at Deliverance Evangelist Church at 20th and West Lehigh Avenue, relatives said. He was up for retirement this year. His mother was notified of the death while she was at work. Ramsey said she told him she'd never dreamed she'd be thinking about funeral arrangements for her son today. Some family members were notified by Walker's uncle, Stephen Cassidy, a lieutenant in the 18th district.
Mayor Michael A. Nutter's office announced that he had ordered that all city flags be lowered to half-staff in Walker's honor. He asked residents of the city to offer police officers their condolences and help with the investigation. No arrests in the murder had been made Saturday afternoon.
Mayor Michael A. Nutter has issued the following statement on the death of Philadelphia Police Officer Moses Walker Jr.:
"For the third time this year, Philadelphians and members of the Philadelphia Police Department have been visited by tragedy with the violent death of a respected, veteran police officer," Nutter said in a written statement.
He referred to the deaths of Officer Brain Lorenzo, who was killed as he drove home from work July 8 by an alleged drunk driver, and of Officer Marc Brady, who was fatally injured by a car while riding his bicycle.
Nutter called Walker "a committed public servant, beloved by his family, friends and colleagues. Our condolences and prayers go out to all of them as they cope with their grief in the loss of this good man."
A graduate of Ben Franklin High School, Walker graduated from the police academy in 1993. He had been in what is now the 22nd District since 1994.
Ramsey said Walker was walking westbound on Cecil B. Moore Street just before 6 a.m. today when he apparently encountered a suspect, or suspects, near 20th Street with a gun.
Ramsey said he did not know the details of the fatal encounter, but it appeared that robbery might have been a motive. Walker had been shot at least twice in the chest and abdomen and was in critical condition.
It was not clear whether the officer had fired any shots in return. Walker was not wearing his uniform at the time.
Walker finished his shift at the 22nd district at 17th Street and Montgomery Avenue and was preparing to leave for a bus stop. Ramsey said a co-worker offered him a ride home and he declined saying, "It's a nice day. I'm going to walk."
The suspect fled south through a vacant lot and a K-9 unit was called in without success to track him.
Ramsey said the type of gun used to shoot the officer was still unknown. A backpack and wallet found at the scene were believed to have belonged to the officer.
Police believe they have a witness, and are talking to others.
Walker was what is known as a 'turnkey' who monitors a holding cell room at 17th Street and Montgomery Avenue. He was about four blocks from work when he was shot and police believe that he was walking to catch public transportation.
The turnkey officer works in the cell and fingerprints, photographs and processes prisoners after they are arrested.
"Obviously the officers are very upset at the loss of our brother officer," said Sgt. Gregory Caputo, of the 22nd district.
"It's unbelievable. It's tough," Ramsey, who was wearing running shoes and civilian clothes, said of the loss. "We literally just removed the mourning bands from our badges last week for officer Lorenzo."
Seawright said her nephew never worried about being killed on the job. "He was always kind and sweet and well mannered," she said.
At the scene, officers and homicide detectives continued late morning looking for evidence. A car parked near where the officer's body was found was taken away. An officer said the car wasn't involved in the crime but it was being dusted for possible prints in the event the shooter came near it.
At the 22nd district at 17th and Montgomery, an American flag was flying at half mast for officers who had previously lost their lives.
Police are asking area business for any surveillance footage that might help.
A $20,000 reward has already been posted for information in the officer's murder. The Fraternal Order of Police offered an additional $10,000 reward.
Police are asking anyone with information to call 215-686-3334 or 3335.
"Somebody knows who did it. Somebody knows what happened," Ramsey said. "They need to come forward."
Staff Writers Morgan Zalot and Jonathan Lai contributed to this article.