An Amazon employee who was leading efforts to unionize workers in Staten Island is taking legal action against the company for firing him last month.

Rashad Long, who worked the overnight shift at Amazon’s new warehouse in New York City, was fired last month by one of his managers for a safety violation, according to a complaint Long filed Wednesday with the National Labor Relations Board, a federal agency that enforces fair labor laws.

In his complaint, which was first reported by the New York Times, Long said that terminating him for a safety violation was just a cover for the real reason: Supervisors were punishing him for speaking out about working conditions at the warehouse.

Amazon warehouse employees announced in December they were trying to organize with the Retail, Wholesale, and Department Store Union. Long was the most outspoken about his frustration at work. During a press conference in December and in media interviews, Long accused managers of forcing employees to work 12-hour shifts five or six days in a row. He said the company treated workers like robots, and he felt unsafe in the warehouse.

Two months later, on February 8, Long broke a minor safety rule when he picked up an item that had fallen off a robot and put it back on the machine, an attorney for the labor union wrote in the complaint, which was shared with Vox.

Long was fired “for engaging in protected, concerted activity by speaking out about the abhorrent working conditions at the Amazon fulfillment facility located on Staten Island,” the complaint said.

Amazon denies the accusation.

“Mr. Long’s allegations are false,” Rachael Lighty, a spokesperson for Amazon, said in a statement to Vox. “His employment was terminated for violating a serious safety policy. All employees, including Mr. Long, are trained from day one on the importance of safety and their role in maintaining a safe workplace.”

The dispute is the latest twist to the ongoing labor standoff between the world’s largest retailer and employees at the company’s fulfillment centers. Amazon has fought past union drives at its warehouses in Europe and has quashed past efforts in the United States. The outcome of the Staten Island workers’ effort to unionize could have a far-reaching impact on blue-collar workers across the country, building momentum for others to follow their lead if they succeed, or dampening enthusiasm if they fail.

Workers have a right to discuss working conditions without retaliation

The National Labor Relations Act of 1935 gave US employees the right to organize and to complain publicly about their working conditions. The labor board investigating Long’s complaint will have to decide if Amazon has enough evidence to prove that Long was fired because of his work performance. If the board determines that it was actually a pretext to punish him for organizing, Amazon may end up having to reinstate him and pay back wages for the income he lost.

In December, Long and several coworkers at the company’s warehouse in Staten Island announced their plan to unionize with organizers from the Retail, Wholesale, and Department Store Union. That union is also working with employees at Whole Foods, a grocery chain now owned by Amazon.

Workers said that negotiating a labor contract with Amazon is the only way to force the company to improve their pay, benefits, and working conditions. At a press conference outside New York City Hall in December, employees shared a list of complaints. Long, who started working there in October, said managers make employees work long, brutal shifts, with little time to rest.

“It takes me four hours every day to get to and from work. Between my work schedule and my commute, I haven’t seen my daughter in weeks,” Long said in a statement one of his colleagues read during the conference.

Long’s coworkers nodded as he described feeling unsafe at work. He specifically mentioned that the warehouse’s sprinkler system and smoke detectors are broken — a hazard that could endanger their lives if a fire breaks out.

But the most disheartening part of his complaint was the suggestion that employees feel less valued than the robots nearby.

“The third and fourth floors are so hot that I sweat through my shirts even when it’s freezing cold outside,” Long said. “We have asked the company to provide air conditioning, but the company told us that the robots inside cannot work in the cold weather.”

Amazon Staten Island worker Rashad just finished a 12 hour shift. He was so exhausted just making it here after working that long with out a real break that one of our organizers Kim shared his remarks. WATCH NOW: Posted by Retail, Wholesale and Department Store Union (RWDSU) on Wednesday, December 12, 2018

Vox was one of several media outlets who quoted Long’s comments, and I reached out to Amazon to let the company respond to employees’ specific complaints.

Lighty (the Amazon spokeswoman) disputed Long’s allegations at the time. She said the Staten Island warehouse has a fire director on site to make sure the sprinkler system and smoke detectors are working as required by law, and that employees are not allowed to work more than 60 hours a week. She added that the warehouse temperatures are regularly monitored to make sure they remain around 73 degrees Fahrenheit.

The move to unionize comes at a tense moment for Amazon. The company faced fierce criticism for its plan to open a second headquarters in New York City — a decision that was made with no public input and that would have cost local taxpayers billions of dollars in subsidies. The backlash from labor activists and community groups, including the labor union working with warehouse employees, contributed to the company’s decision last month to scrap its plans to open an East Coast headquarters in the city.

The online retailer is also dealing with serious complaints from employees, who describe harrowing work conditions and low pay at Amazon’s warehouses in the United States and across the world. In July, Amazon workers in Europe went on strike to protest what they described as hot, windowless, soul-crushing work environments.

In November, on Black Friday, workers at Amazon warehouses workers in Spain, Germany, and France organized strikes, and protests were held in Italy and the United Kingdom. Workers in the US are getting restless, too.

Lighty has said that the company respects its workers’ decision to join a labor union, or not. In an email to Vox on Thursday, she said Amazon already provides workers with competitive pay and benefits, pointing out that employees in the Staten Island facility earn between $17 and $23 an hour.

“We encourage anyone to compare our overall pay, benefits, and workplace environment to other retailers and major employers in the community and across the country,” she told me.

Amazon employees need to take a few more steps before they can officially form a union, though. A majority of employees in their workplaces need to sign union membership cards, to show their support for collective bargaining. If that happens, the company can voluntarily recognize the union.

If the company doesn’t want to recognize the union, then workers will have to hold an official unionization vote through the National Labor Relations Board, an independent federal agency that enforces US labor laws and collective bargaining rights. If a majority of employees vote in favor of unionizing, then Amazon is legally required to recognize the union.

Then, finally, they can begin to negotiate a labor contract.