John Malloy Jr. was sitting at his breakfast table in the city's Holmesburg section around 7:30 Friday morning when he heard the gunfire: three quick shots – "bam, bam, bam" — then a fourth about 20 seconds later.

Malloy said he called 911, unsure if the shots came from his neighbor's house or the alley behind them. Moments later, he said, a woman who worked as a nanny watching the twin girls next door knocked on his kitchen door. She was hysterical, Malloy said.

Police arriving at the brick home on the northeast corner of Meridian and Erdrick Streets found a grisly scene: In an upstairs bathroom, Linda Rios-Neuby, a well-known and -liked City Hall staffer for two decades, lay dead from three gunshot wounds. Near the front door, with a single shot to the head, lay her husband, Haywood Neuby Jr.

Investigators said the couple had separated in recent weeks, and that Haywood Neuby had stopped by to see his children, but the visit turned into a deadly argument. Homicide Capt. Jack Ryan said Rios-Neuby was the 21st woman slain in a domestic killing in the city this year, up from 14 at this time last year.

"I can't frankly come to terms with what we call someone who orphans their children and kills the mother of their children," Ryan told reporters at a briefing. "It's unbelievable the kind of madness that would seize someone to commit such an act."

Rios-Neuby, 37, was a familiar face in City Hall, first hired as a teenage summer intern and rising to head of human resources for City Council. The stunning news of her death, and the circumstances around it, moved swiftly through government offices.

"Linda was the behind-the-scenes backbone of everything that Council ever did," said Councilwoman Maria Quiñones-Sánchez.

Mayor Kenney, who worked with her during his own Council tenure, remembered her as a "dedicated public servant."

Another Council member, Curtis Jones Jr., said that "in an office full of nice people, she was the nicest. She was like a cup of coffee in the morning when you saw her."

At the news briefing, Ryan said police had been called to the home for an argument in June, but no one was arrested.

By mid-morning, dozens of people had gathered on corners near the scene of the killing, a residential neighborhood of two-story brick twins with sloping front lawns. Some cried; most didn't want to talk. "Now is not the time," one woman said.

Malloy, whose kitchen shares a wall with Rios and Neuby's home, said he had previously heard them argue but it was "very rarely."

He said he and his wife have been living in their home for 45 years and Rios and Neuby moved next door in 2008. He remembered the year because, he said, it was before the Phillies won the World Series.

"They were very good with the kids," he said. "They were both very watchful."

Malloy's son, John III, who also lives in his home on Meridian Street, said the couple's nanny told him that Rios-Neuby and her husband had separated two weeks ago. After the shooting, he said, the couple's twin girls walked, crying, across his lawn toward his side kitchen door. Later, he said, one told him: "My parents are dead."

Ryan said relatives had come to take care of the girls.

In a 2013 tweet, Council President Darrell L. Clarke  congratulated Rios on her pregnancy.

On Friday, he mourned her passing.

"I will have more to say in the future about the role of guns in this tragedy, and the scourge of domestic violence, but for now I join my colleagues and all City Council staff in mourning this tremendous loss," Clarke said in a statement. "It will take some time, but I'm going to try to remember Linda at her happiest — her beautiful smile and infectious joy as she carried those beautiful twins four years ago, never slowing her pace at work until nature forced her to do so."

Jocelyn Vazquez, 33, cousin of Rios-Neuby, said the couple had known each other since high school and married about 10 years ago. She said she believed Neuby, 43, worked as a counselor for youths who live in a group home in South Jersey.

Vazquez said she was not aware of any problems between the two.

The shootings "blindsided us," she said. "We're trying to figure out what happened."