"My son served. He served everybody. He served his city. He served his family. He served his nieces and nephews," she said.
"I want to thank God for my son," she said. "That's all, that's all I have to say."
The vigil, which Police Commissioner Charles H. Ramsey and more than a dozen fellow officers attended, drew sorrow and anger from Walker's relatives, who prayed in a cluster. They came from as far away as Baltimore and Virginia. One nephew sobbed uncontrollably and had to be escorted from the area.
Ramsey, in an interview, said authorities didn't have any suspects or "anything really concrete" but were working the case hard.
"They'll close it, there's no question in my mind, they'll bring it in," he said.
Police have not ruled out the possibility that more than one person was involved in the slaying.
Walker, in civilian clothes, was shot three times, including in the chest and abdomen. Preliminary examinations of his service revolver did not indicate it had been fired, according to Officer Tanya Little, a department spokeswoman.
Walker appeared to have drawn his gun, as it was found unholstered under his body.
Ramsey said, "One of his bullet wounds was to his hand, which looks like, as he was coming out with his weapon, he got struck there."
Police were working with Walker's relatives to determine whether anything was missing from his backpack and wallet, both recovered at the scene of the killing.
The nighttime vigil book-ended an emotional day that started with a service at Walker's church.
Lucille Brown, 73, stood outside Deliverance Evangelistic Church in North Philadelphia, hesitant to enter the sanctuary where she used to sit with Walker.
"I'm a little hesitant to sit down, [that's] the reason I'm out here," she said. "I'm going to go sit down where he used to sit next to me every time."
Brown said Walker's seat in church was left empty out of respect by the regular churchgoers.
She met Walker about 15 years ago at Walker's previous church at 30th Street and Girard Avenue in Brewerytown. When that church closed, Brown invited Walker to join Deliverance, telling him it was a family where he would be welcome.
Walker never showed up in uniform, and he had a level of modesty and humility that left some churchgoers surprised to learn their friend was a police officer, she said.
"He never pushed anyone around, you would never know he was a cop," Brown said. "He was not the flashy kind."
The two friends interacted largely through the church, with occasional dinners or events outside it. They would "laugh and talk about weight," Brown said, because Walker had accomplished a goal of losing weight. Brown had met Walker's mother and family, and she talked to some of them on Saturday by phone.
The Rev. Michael King spoke briefly about Walker at the service.
"We want to cover his family with prayer," King said. "Come against this demonic spirit that's going through our city, this violence. . . . We need to take a stance against all this violence that's going on in our cities."
King asked for a moment of silent prayer for the families of Walker and other slain police officers.
"We have police officers right here in our own church," King said. "We pray that God will cover them with his protective blood, keep them protected."
Sunday evening, Ramsey held Wayne Walker's hand and pointed out where the killing took place. Other officers stood in the middle of Cecil B. Moore, at attention, to show respect.
Wayne Walker sobbed, "Oh Jesus." Her youngest child, Kenya Boulware, 23, leaned over to kiss her. Another son held her close.
During the vigil, Moses Walker's brother Anthony said that the violence needed to stop and that the shooter would be caught.
"My brother ain't hurt nobody. Anybody that know my brother know he's all about love," he yelled amid sobs.
"I love my brother and I know my brother's looking down on all of us, and I know he's hurting because we're hurting. All these cameras and all this don't mean nothing. My brother is gone and he's not coming back."
Outside the prayer cluster, away from the candles, Boulware spoke to news cameras, reading from a multicolored notebook. She had written her speech shortly before the vigil. It ran fewer than a dozen lines.
She took a deep breath before speaking and said her brother was a dedicated family man and officer.
"He's dearly loved and will be dearly missed," she said, looking up to the cameras every few words.
A few minutes later, she knelt on the ground. She bent over, sobbing, with her hands over her face as relatives comforted her.
Police ask anyone with information on the killing to call 215-686-3334 or 3335. Tips can also be sent anonymously through the www.phillypolice.com website.
Contact Darran Simon at 856-779-3829, firstname.lastname@example.org, or follow on Twitter @darransimon.
Inquirer staff writer Linda Loyd contributed to this article.