Roughly 8,400 grocery workers went on strike early Wednesday at dozens of Kroger-owned stores in Colorado after talks broke down over pay and working conditions, union and company representatives said.

The negotiations have never gotten as far as a proposal that could be put before King Soopers workers for a vote. The union turned down Kroger's final offer, which would have boosted starting pay to $16 an hour and raised the hourly rate by as much as $4.50 in the first year. It also included ratification bonuses of $4,000 for workers with at least 10 years of experience, or $2,000 for more recent hires. The grocery chain, in turn, rejected a union plan that included a $6 per hour wage increase and new security requirements - a request made in the aftermath of a mass shooting that left 10 people dead at a King Soopers store in Boulder last year.

The walkout is the latest pushback by workers who've toiled through pandemic conditions, staff shortages and supply chain tie-ups while their companies have recorded soaring profits. In the last year, scores of strikes have been authorized, including by Kellogg's, Nabisco and John Deere workers, as part of a new wave of labor activism.

In a statement, Kim Cordova, president of the United Food and Commercial Workers local chapter in Denver, accused the company of enriching its bottom line on the backs of store workers who have risked their lives during the pandemic.

"King Soopers is enjoying record profits while leaving its workers to struggle with low wages," Cordova said. "Grocery workers ensure that our communities have access to food, but they cannot even afford to feed their own families. This is grossly unfair."

But Kroger contends the union is "reckless and self-serving," accusing union officials of acting "without regard for the implications to associates and Coloradans," in a Wednesday news release.

King Soopers president Joe Kelley accused Cordova of denying workers the right to vote on the company's most recent contract offer. "Local 7 is putting politics before people and preventing us from putting more money in our associates' pockets," Kelley said in a statement.

In Denver, workers lined up to begin picketing before daybreak on Wednesday. In interviews, they said they joined the walkout over concerns about wages, security and more.

Liz Wesley, a floral manager at a King Soopers in Colorado Springs who joined picketers in Denver, said she's had a hard time retaining workers because entry-level wages have risen quickly at nearby fast food restaurants.

The 17-year employee says her King Soopers job made it possible to buy the home where she raised two children. But newer hires have trouble meeting the cost of living, and the company's raises haven't kept up. She says she is aware of colleagues who are homeless or live in their cars.

Wesley says she started at about $16 per hour in 2005 and makes about $20.50 today. Her pay edged up 35 cents an hour each of the last three years, she says.

"We can't afford to live in the communities that we serve anymore," Wesley said.

She also expressed concerns about security in her store, recalling how a pharmacy technician was held up at gunpoint. Another King Soopers, in nearby Boulder, was the site of a mass shooting last summer that left 10 people dead, including three store employees.

The union, in a Jan, 6 proposal, sought a slate of guarantees meant to protect workers and customers from a mass casualty event. The union sought semiannual trainings on how to recognize a potential emergency and de-escalate when possible, along with detailed evacuation plans for a worst-case scenario.

The proposal included language saying workers don't bear any responsibility for protecting merchandise during an emergency. It also would have required the company to have an armed guard present at every store when employees are on duty. And the company would be obliged to pay for trauma counseling following any event labeled a "dangerous emergency," defined as an incident that could or does result in mass injuries or deaths.

Steve Ponzio, a produce clerk at a King Soopers in South Denver, says his store never had any armed security until after the union authorized a strike on Jan. 7.

"There's security now, all the stores have security now, as of about a week ago," Ponzio said. "There were no security guards in the stores before that."

A Kroger spokesperson did not speak directly to the state of the company's security efforts, other than to promise to support workers when they feel unsafe.

"We care about our associates, and we have always supported associates when a tragedy or an emergency situation has occurred, and we always will," a Kroger spokesperson said. "As an organization, we remain committed to creating a safe shopping environment and supporting our associates with on-demand access to mental health resources as well as personal safety training."

The spokesperson urged the union to allow workers to vote on one of its offers. "We respect our associates' right to choose and the [union] should do the same," the Kroger spokesperson said.

The company intends to keep its 77 stores in the state open despite the walkout. "We have contingency plans in place, and team members from across the country have traveled in to support efforts coupled with the hiring of temporary workers," a Kroger spokeswoman said in an email.

Kroger is one of the nation's largest retailers with $132 billion annual sales. It operates roughly 2,750 grocery stories under 25 brands, including Harris Teeter, Fred Meyer, Ralphs and Food 4 Less. It had net earnings of $483 million in the third quarter of 2021, driven by a 14% increase in sales over two years. In June it announced a $1 billion stock buyback program, according to MarketWatch.