Faced with a startling rise in homicides in the city this year, Philadelphia police are adding investigators and adapting their methods to confront the trend, officials said Tuesday.

Seven people were killed within 24 hours Monday, including a 15-year-old mistakenly targeted by neighborhood gunmen and a mental-health counselor who worked with some of the city’s most vulnerable populations.

As of Tuesday, 62 people had been killed in Philadelphia during the first five weeks of 2021, an increase of 55% over last year, and double the average of the last 14 years, according to department data.

In addressing those killings Tuesday, Homicide Division Capt. Jason Smith said the trend has upended traditional assumptions about crime cycles, including that most murders happen at night or on the weekends. Instead, he said, fatal shootings are happening at all hours, even in daylight, and some are being telegraphed hours before on social media.

“It could be a Thursday, it could be a Monday; historically you would think it was Fridays and Saturdays,” Smith said. “... Homicides are occurring on all tours of duty.”

The violence Monday was spread across the city between 1 a.m. and 8 p.m., with two separate double homicides in Kensington and Crescentville, as well as fatal shootings in South Philadelphia, Olney, and East Falls, police said.

» READ MORE: Separate Philly shootings leave 7 dead in a day

Smith said detectives have made arrests in at least two of the cases — the double murder of Thomas Burnett, 61, and Maurice Harper, 42, in Kensington and the shooting of Christine Gibson, 54, the mental health counselor who was found shot dead inside her office in East Falls.

He declined to identify the suspects but said charges in both cases were expected to be filed later Tuesday.

The rest of the cases, Smith said, are “moving in a good direction.” Police identified some of the other victims killed Monday as Jehesel Garcia and Steven Williams, both 24, found shot inside their home in Crescentville, and Darius Winters, a 15-year-old killed in South Philadelphia.

The identity of the seventh victim, a 25-year-old woman killed about 2:15 p.m. Monday on Rubicam Street in Olney, was not released.

Monday’s tally of violence is emblematic of an upward trend that has plagued Philadelphia for about six months. Before June, the city had not recorded more than 180 shooting victims in a month in at least 13 years. But from June through November, at least 200 people were shot every month, police statistics show — an average of nearly eight people per day.

Police Commissioner Danielle Outlaw, in addressing the media Tuesday, said COVID-19 had presented officers with a challenge by keeping more people indoors, driving crime out of sight. And, she said, the mask requirements of the pandemic added to the difficulty of identifying suspects by obscuring their faces.

The department has shifted more focus to social media. Suspects in recent killings have at times announced their intentions in real-time, Outlaw said. She added that the homicide division has added four investigators to its ranks since October, to help combat the upward trend in violence.

Two homicide investigators visited Catherine McMillan at her home in South Philadelphia on Tuesday morning. Hours earlier, Darius Winters, 15, was gunned down while sitting on her stoop, catching up with her 19-year-old son and a friend.

McMillan, 38, said her son and his friends “are not street children” and are not involved in gangs. Police on Tuesday called Winters an “innocent victim that was targeted incorrectly.”

“I just need people to know that,“ McMillan said, standing next to the bullet-scarred gate of her Hollywood Street home. “They didn’t do anything wrong and this was not a retaliation against them.”

Nevertheless, she said, the shooting left her determined to move.

”We’re getting out of here. We’re getting out,” said McMillan, who also has a 15 year-old daughter and 7-year-old son at home. “This is no place to raise children at all.”

At the other end of the city, where Christine Gibson was found dead inside the offices of United Peers, a recovery center for people with mental health disorders, residents and business owners alike were stunned by the shooting.

» READ MORE: Philly’s violent year: Nearly 500 people were killed and more than 2,200 shot in 2020

“It’s unusual for this area, particularly in such a public, high-traffic area,” said Greg Skochko, a physician who owns a primary care clinic on the block. “I’ve never had concerns before, and I’ve been here five years.”

United Peers, which is housed on the ground floor of a building at the corner of Ridge and Midvale Avenues, was closed Tuesday and yellow police tape was still strung in front of a side door.

Reflecting on Gibson’s death, Skochko said: ”This is even more heartbreaking because she was trying to help people.”

Staff writer Julie Shaw contributed to this article.