Gardening under the tobacco tree in her backyard one day in June, Mercy Vanaman felt something rough in the dirt. She clawed at the soil, then pulled up a tarp and discovered a black duffel bag half-buried in the ground. She had found evidence of unwelcome visits to her West Oakland garden before — usually by people, usually at night. In that way, the garden was a kind of secret hiding place.

But this time, she pulled open the bag’s zipper and gasped.

Inside was an assault rifle, shotgun shells, a black ski mask, black gloves and a towel. Vanaman’s heart raced as she stared at her discovery and tried desperately to figure out what to do.

Then, she called the police. It was, she thought, “the right thing to do.”

When two Oakland police officers showed up to retrieve the guns, Vanaman remembers one of them turning and telling her: “The gang isn’t going to like this.” And then the police were gone.

“Shaking like a leaf … Absolutely terrified … Need a hug,” she wrote on her Facebook page.

In the coming days, Vanaman experienced a scourge that’s plaguing Oakland’s streets and perpetuating the violence as much as any gun or drug deal: She became a victim of intimidation.

At first, the gang members who came looking for the guns demanded money: $800 in a week. Then, they threatened her with rape, torture, death.

If anyone could help her, Vanaman thought, the police could. Yet in the aftermath of her discovery, she, along with five housemates, had to flee her home of seven years, hiding with friends and searching for a way out of a frightening dilemma that in Oakland even the very authorities sworn to protect her can’t seem to solve.

Seven weeks later, she is still too terrified to return home.

Intimidation abounds

Every year in Oakland — and to some extent in other high-crime parts of cities such as Richmond, East Palo Alto and San Jose — hundreds of people find themselves in situations like Vanaman’s, and sometimes much worse. Intimidation is an old tactic, but one that is constantly being reinvented in fresh and outrageous ways.

In Oakland, interviews with crime victims, prosecutors and police show, the result is a community increasingly afraid of itself, bullied into silence by its most ruthless and violent members.

“I don’t believe citizens should become hostages in their own communities,” Oakland police Chief Howard Jordan said in a recent interview.

Yet, in Oakland, that is precisely what is happening.

Often the intimidators are hardened criminals trying to cover their tracks. Authorities describe how slaying suspects from jail dispatch friends to make sure witnesses don’t show up to trials.

In November, an Oakland jury convicted Gumaro Baez of murder and dissuading a witness after he shot two men in a vehicle, then executed two young girls in the back seat — just because of what they had seen. In a letter read during Baez’s trial, he described the 2008 killings to a fellow inmate, explaining his motives for shooting the girls:

“If the broads were still alive, it would’ve really been over,” Baez wrote. “Everybody know you can’t leave witnesses.”

Two former members of Oakland’s Norteño gang acknowledged in an interview with this newspaper that they had actively participated in intimidation tactics to keep enemies or potential witnesses quiet.

“You go get them, you stuff them in your trunk and beat them,” said one of the former gang members, Ernesto, who asked to remain anonymous for safety concerns. “You do whatever you need to do to shut them up.”

Sometimes, where you live is enough to turn you into a victim. This year, a gun-wielding drug dealer threatened to kill 39-year-old construction worker Craig Lima in front of his West Oakland house — just blocks from Vanaman’s home — as he tried to shoo away the dealer.

Oakland Housing Authority spokeswoman Greer McVay said even police patrolling the city’s housing projects are “routinely threatened.”

Becoming the norm

While intimidation varies widely, the tactic, inside prison and out, is becoming increasingly dangerous and commonplace, law enforcement officials and academics say.

Richard Frei, a Philadelphia psychology professor who has written about intimidation and testified before a Senate subcommittee on crime and drugs, describes how a “no-snitching” culture is spreading in cities across America.

“What was once a code among thieves, and then a code of the streets, is quickly becoming a societal norm,” Frei wrote.

According to a 2006 study by the Center for Problem-Oriented Policing, prosecutors estimate that witness intimidation “plays a role” in more than three of four violent crimes in gang-dominated neighborhoods.

“There’s some element of intimidation in every case I see,” said prosecutor John Brouhard, who oversees the Alameda County District Attorney Office’s gang task force.

Prosecutors can charge intimidators with felonies such as dissuading a witness, punishable by up to four years in prison, and tack on enhancement charges that can lead to life sentences. Last year, witness intimidation prosecutions in Oakland rose to 44, a 10-year high. But that doesn’t come close to stopping the problem on the streets because most victims and witnesses are afraid to come forward.

“I sympathize with these people who say they can’t talk because they’re afraid of getting killed,” said Oakland police Sgt. Mike Gantt. “I know I can’t tell them much that will make them feel better, or make their lives easier.”

Gantt remembers years ago trying to persuade a woman to testify after she witnessed a man kill her child’s father. But she backed out, terrified after the man’s girlfriend threatened her.

“I’ve seen people get maimed,” he said of witnesses. “One lost an eye, paralyzed, shot, their parents got beat up, houses robbed, families beat up, and, worst case, murder.”

The dead-end gang

For Vanaman, the decision to call police immediately after her discovery in June wasn’t easy. The drug dealers who hung out near the dead end of Henry Street were just teenagers. One afternoon last summer, in an effort to make friends, she brought them a bottle of Malibu rum. They took it, but laughed; Malibu was cheap, they said, and they were worth more.

But in a way, they respected her, too. Because she took in so many stray cats and often dressed in black, the gang called her “Cat Lady” and jokingly asked her questions about witchcraft.

From her garden perch, Vanaman had plenty of time to observe the gang’s comings and goings. She knew they used neighborhood houses to hide crack and heroin. If a police cruiser came a little too close, spotters would send a text message and shout “Five-O.”

“Suddenly there’d be guys running through the yard and hopping the fence and grabbing drugs out of the recycling,” said Vanaman, who lives off disability from a series of lingering childhood medical issues and acted as an unofficial property manager at her rental house. Every walk of life came to buy.

“Two for 15, two for 15,” she heard the dealers yelling the price for baggies of crack, as young white kids in fancy cars slipped them bills and drove away.

By the time she found the duffel bag, she had finally begun to feel at home in the gritty yet rebounding neighborhood of historical Victorian houses. With easy access to BART, it began attracting young professionals like the teacher, the actor and the fashion designer who rented rooms in the same house.

But the danger was clear. Over the years, Vanaman had found four bullets around the house, one in the garden and three lodged in basement walls.

Vanaman tried to strike a balance. She posted a note on the refrigerator advising her housemates to call police if more than three men loitered around the house. Police records show two calls for service from her address in the past 12 months, but records Vanaman obtained from Sprint show nine calls to police within the two weeks before she discovered the guns.

Vanaman and her housemates say they called police over the years dozens of times but nothing changed. The police rarely came. And the boys on the street continued to do their thing. Three housemates left because of the violence, and three new ones moved in.

“In the last year it just got increasingly awful, just frightening,” said Daniel Lovejoy, a special-needs teacher and one of Vanaman’s housemates. “But we never expected it to get to the point of having assault rifles in our yard.”

A tough choice

Chief Jordan has repeatedly called on citizens to make the difficult choice to speak up when they are victims or witness crime in their neighborhoods. “I ask you to stand with me and with our community leaders here today to make our city safer,” he said in February after five people were killed and 15 more wounded by gunfire in one week in Oakland.

The chief said he understands how cooperating with police can be dangerous, so the best alternative is often for witnesses to remain anonymous through texts, emails or tip lines. However, that wouldn’t have helped Vanaman, a 30-year-old former foster child.

If people like Vanaman do step up, Jordan said, there should be a “reasonable expectation” that police will protect them.

“If she brought in a bag of guns and said it belongs to X, Y or Z, and that she’s not comfortable going back, then, yeah, we have an obligation to be proactive in helping her,” Jordan said.

But it’s tough to provide meaningful help in a case like Vanaman’s. Police and prosecutors can tap into federal and state programs to relocate and assist witnesses, but those are usually reserved for major crimes. California spent more than $4 million on such efforts in 2010-11. In one of those cases, authorities relocated an Alameda County man who had been shot by two men trying to stop him from testifying against a group who had shot at a police officer.

Police have pledged to step up patrols near Vanaman’s former house at Eighth and Henry streets and are investigating the source of the duffel bag. Beyond that, they say, the reality is they can’t respond to every call.

“As much as I’d like to be there for what Mercy needs, we just don’t have the resources right now,” said Officer Sekue Millington, a West Oakland “problem-solving officer” familiar with Vanaman’s case.

Like many cities struggling to balance their budgets, Oakland has fewer police officers on the streets: The department has 641 officers, almost 25 percent fewer than it had in 2008; only 250 are on patrol to respond to about 87 serious crimes a day.

The threat

On the Friday she discovered the duffel bag, Vanaman alerted her housemates and suggested they leave for a couple of days. Let things cool off, she told them, hoping it would blow over. She spent the weekend in San Francisco with friends. Before leaving that night, she noticed two guys standing in front of the house, pointing to her garden. They didn’t look happy.

When Vanaman returned, four young men stood in her frontyard. “What did you do with the guns?” one of them asked.

“I called the police,” she told him. “I didn’t know what to do. I’m sorry.”

The man scowled and told her she owed him $800 and said she had a week to come up with the money. “I don’t make that much,” she replied.

“Bitches get killed for that,” he told her. “Bitches get tortured for that.”

A keen observer of others, Vanaman noticed the young man used the passive voice so she couldn’t accuse him of threatening her directly. But the implication was clear. “Bitches get raped for that,” he shouted.

Suddenly, she felt torn. For years, she had rationalized her choices in coping with the danger outside her door. Now, she knew turning in the gun was the right moral decision, but it had put her life at risk.

With the man still berating her, Vanaman said she would sell whatever valuables she could to get the money. Then she turned and fled into the house.

“We need to go,” she told her roommates. “We need to go now.”

“Then we ran for our lives,” Vanaman recalled recently in an interview at a San Francisco coffee shop. “We put as much as we could on our backs and we ran.”

That night on her Facebook page, she asked: “Does anyone have an extra $800 laying around?”

No way out

On the first Saturday in August, a police officer escorted Vanaman back to the house so she could box her belongings and leave for good.

She isn’t the only tenant who has left the two-story powder-blue Victorian with yellow trim; most have moved out, but not before a couple of them tried to strike a deal with the gang, saying Vanaman shouldn’t have gone to the police in the first place.

“It’s only because I got everyone out of that house that we’re not raped, tied up and dead,” Vanaman insisted. “Anyone who’s got a bag full of AK-47s means business.”

Vanaman said police have done little to comfort her, besides standing sentry as she packed up her belongings. And that underscores how defeated and overwhelmed many have become in the battle to take back the most crime-ridden parts of Oakland.

Even Vanaman knows that with so much crime in so many corners of the city, protecting just one resident, who did what seemed so obviously like the “right thing,” is nearly impossible in one of Oakland’s most dangerous areas.

Now, for calling police after discovering a gun buried in her garden, Mercy Vanaman is once again looking for a place to call home.

Contact Scott Johnson at 510-208-6429. Follow him at Twitter.com/scott_c_johnson and Twitter.com/oaklandeffect.