For the second year in a row, Oakland is the Bay Area’s epicenter of a pandemic-fueled spike in homicides.

Data requested by The Chronicle from the region’s 15 most populous cities showed the largest rise in Oakland, which logged 102 killings in 2020, and 124 last year (we include killings that meet the FBI definition of criminal homicides). Other cities remained relatively stable, though several have not recovered from a burst of violence that coincided with COVID-19 and the economic shutdown. The total number of killings in the 15 cities was 295 in 2021, up from 289 in 2020.

San Jose, a city so rattled by mass shootings that its leaders recently passed an ambitious law requiring insurance for gun owners, is now seeing a downward trend — from 44 homicides in 2020, to 31 in 2021. At the same time, small outer-ring cities such as Richmond and Vallejo are struggling to contain relatively high murder rates per capita.

San Francisco witnessed a moderate increase, from 48 homicides in 2020 to 56 in 2021, as residents loudly sparred over crime and policing, and the progressive district attorney stared down a recall election. Still, the city of nearly 900,000 people had a relatively low homicide rate of 6.4 deaths for every 100,000 people. This was slightly less than the combined homicide rate of 7.4 per 100,000 for the the 15 cities combined, and commensurate with Hayward and Fairfield.

But no other city has seen gun violence comparable to Oakland, where five years of progress swiftly unraveled starting in the summer of 2020.

“From May 30 to June 6, 2020, we saw just in that week seven murders,” Oakland Police Lt. Frederick Shavies told The Chronicle, recalling the moment that he and other law enforcement sensed a crisis afoot.

“And then we just continued to see it climb. Thirteen in June. Eleven in July. Sixteen in August. Fifteen in September. Thirteen in October.”

Shavies, who commands the homicide section of the Police Department, had no definitive theories to explain the homicide crisis, though he provided a few observations. Guns are proliferating in Oakland: Police said they seized 1,199 firearms last year, down slightly from 1,272 in 2020 but still up 37% from 875 in 2019. The lieutenant was also troubled to find that people accused of gun crimes appear to be cycling in and out of jail. In 2020, he said, officers arrested six people who had already been apprehended for a gun crime, and released from custody, within the previous week.

Others saw Oakland’s scourge of violence through a different prism. Anne Marks, executive director of the violence prevention nonprofit Youth Alive, pointed out that in prior years, Oakland had outpaced other cities in interventions to decrease violence. Once the pandemic took hold, those programs had to temporarily stop, or dramatically adapt — say, by meeting the city’s highest-risk populations over the phone instead of face-to-face.

“It’s so hard to build a relationship with a mask on, with someone who is paranoid, and traumatized, and can only see part of your face,” Marks said. She described how COVID-19 impeded key violence-prevention work, including hospital visits with gunshot victims or even the ability to take someone to lunch or drive them to a court hearing.

She saw the abrupt shift in Oakland’s trajectory as proof of how successful its violence prevention efforts had been, and how much the city suffered once they were handicapped. Marks hopes the city will turn around in the coming months, bolstered by an infusion of funds to social services and violence interrupters this summer — a plan the City Council approved last year.

Still, people who work in the field remain on edge, watching a ruthless cycle of retaliations.

“At one point I was getting at least three referrals a day,” said Andrea Piazza, an intervention specialist for Youth Alive’s Caught in the Crossfire Program, which works with victims of gunshots or assaults as they recover from injuries and try to get back to work or school. Most of Piazza’s referrals come directly from Highland Hospital, and the people she helps face daunting challenges — from psychological wounds, to severe disabilities that impede them from working.

When shootings reached a critical point, Piazza said she carried up to 19 clients at a time — and those were the ones who willingly accepted services.

Father Jayson Landeza, a chaplain for the Oakland police and fire departments who lives in a rectory at 82nd and Bancroft avenues, said he’s afraid to go outside after dark to take out his garbage.

“There’s this general sense of malaise or despair in the city,” Landeza said on the phone, as he headed to Lake Merritt on a recent Tuesday afternoon. A double shooting had occurred that morning outside the Kume spa on Grand Avenue, leaving one employee dead and another in critical condition. It was the same block where, two months earlier, a gunman shot and killed 27-year-old Eric Davis as he tried to disrupt a car burglary.

“There’s almost a feeling of hopelessness,” Landeza said, with a heavy sigh. “Like, how are we going to get out of this?”

Some criminologists view Oakland as a reflection of larger societal factors. Historically, intense violence is an aberration, not a norm, and it tends to occur when major social disturbances hit already-precarious social networks, UC Berkeley law Professor Jonathan Simon pointed out.

One tragic aftereffect of COVID is the death of elders, who serve as “influencers” in a community and often hold families or neighborhoods together, Simon said. People also had to grapple with closures of schools, recreation centers, and youth sports programs, a dramatic loss of service sector jobs and sudden demands to provide child care for kids who were stuck at home — all of which piles stress on families and may aggravate existing disputes.

The grief and rage associated with the pandemic becomes volcanic in places like Oakland. In some of the city’s neighborhoods, “a history of segregation and extreme economic marginalization have compounded to produce communities that are very vulnerable to violence,” Simon said.

Moreover, homicides are self-reinforcing. Each killing means another vendetta to play out. It also means additional strain on an already overtaxed police force. Last year in Oakland, investigators had 12 cases stacked on their desks on any given day, Shavies said — roughly three times the workload recommended by law enforcement reformers. As a result, it’s become more difficult for police to solve cases, take the most prolific perpetrators off the streets and prevent future retaliation.

“It almost becomes untenable,” Shavies said, attributing the heavy caseloads both to the homicide surge and to attrition from the department.

But the social conditions that contribute to rising violence in Oakland don’t stop at the city’s borders, and some experts argue that it’s not prudent to treat Bay Area cities as discrete territories. Several people arrested for killings in Oakland last year came in from out of town, Shavies said.

Even so, Landeza can sense pain and fear welling up in Oakland — feelings so widespread and powerful, they seem to have made the city more combustible than its neighbors.

“Just listening to the kinds of calls for service on the police radio,” Landeza said. “A lot of stuff going on in homes. Going on in neighborhoods. Road rage. You name it. Every bit of that seems to be part of the dynamic.”

Susie Neilson and Rachel Swan are San Francisco Chronicle staff writers. Email: susie.neilson@sfchronicle.com, rswan@sfchronicle.com Twitter: @susieneilson, @rachelswan