She said Citi invited its entire 200,000-person global workforce to a Zoom call in which Mr. Corbat discussed his long friendship with Mr. Mason -- the two had played golf together and knew each other's families well. Mr. Corbat said he had always considered himself colorblind, but told employees he regretted not asking Mr. Mason more questions about his life, Ms. Wechter said.

"Even our CEO was willing to say he probably got parts of this wrong, and it's OK to get parts of this wrong," she said.

Since the post, Mr. Mason said many colleagues have asked him what they can do to help. He said he has proposed ideas, but also emphasized that relying only on black executives won't be sufficient. "There aren't enough of them in most companies to change the fabric of the organization," he said.

'Put Up This Wall'

Nathaniel Patterson, Jr., 64, a leadership coach who serves on board of the Mobile Area Chamber of Commerce and other nonprofits, didn't even tell his mother about the time he was 14 years old and walking home from school when a police officer pressed him up against a car and asked what he was doing in the neighborhood.

"When I didn't answer, he threw me to the ground and put the gun in my mouth," he said. "He told me that 'I could kill you' and nobody would blame him. He told me that before I could go, I had to suck on the barrel."

He buried it away from his colleagues during his years as a marketing executive and later running his own marketing firm until earlier this month, when he told the story in a LinkedIn post to hundreds of contacts and colleagues. "You put up this wall," he said. "If you are labeled as a person bringing up the race card, you are going to have your career blocked."

Lynnwood Bibbens, 48, the co-founder and CEO of streaming video network ReachTV, said he never brought up his run-in with police to his wider professional network before. "You hear people saying already that black people think they are victims," he said.

On June 2, he wrote a letter -- opening with "Dear America" -- describing the 2004 encounter with police officers who pointed a gun at his head after pulling him over in his Mercedes. He said they held him in handcuffs for nearly an hour on the side of the busy street in Cherry Hill, N.J., near the office where he ran a business with 40 employees. Police later told him that his car matched the description of a stolen vehicle.

"I honestly thought I was going to die; I thought about the things I wanted to tell my son and wouldn't have the chance," he wrote in the letter posted on Instagram and later on LinkedIn.

According to the police report, the license plate had been incorrectly entered by another police department as stolen.

"There's a lot of white people that look at me and a lot of successful black executives as not 'black,' " Mr. Bibbens said. "They see black people on TV, and they see me, and they say, those are two different types of black people. They can't have similar experiences. They must have done something different. The truth is, we have similar experiences."

Cara Robinson Sabin, 50, the CEO of Sundial Brands, said employees at the beauty company, which focuses on black shoppers, were already having candid conversations about race. Those conversations are now happening at other brands owned by Unilever PLC, which acquired Sundial Brands in 2017. The depth of the conversations feels different this time, she said.

The pandemic -- and the fact that many people are working remotely, sharing their stories in video chats and conference calls -- is making it easier for some to open up, Ms. Sabin noted, adding: "There's something about looking at people's faces on video that feels more intimate."

'A Turning Point'

After he saw the Floyd video, J.D. Redmon, a 29-year-old vice president of marketing at TTN Fleet Solutions, said he couldn't sleep or concentrate on his job at the trucking-software company in Argyle, Texas. He decided to post a seven-minute video on LinkedIn to urge his co-workers to call out racism and to share his own encounters, including a painful childhood memory of white neighbors moving away when his family moved nearby.

"I was fully prepared to wake up the next day without a job," he said.

A few days later, Mr. Redmon's employer asked him to speak on a Zoom call where other black employees told stories of their own. "It was actually a turning point for black employees at my company," he said. "I think they felt comfortable speaking up because they saw how I was being embraced by my peers."

After he posted another video on Juneteenth pointing out that the trucking industry is led mostly by white men, he said some people inside the company told him he needs to be careful about not offending anyone and warned him that LinkedIn is a professional site, and not for personal views.

But his boss, Tyler Harden, an executive vice president, sent him a text: "Don't ever let anyone or anything change you! That is not a request!"

"If being me costs me my job, so be it," Mr. Redmon said.

Kim Seymour, 50, chief people officer at WW International Inc. (formerly Weight Watchers), said she has long been vocal on issues of race, equality and inclusion as a human-resources professional and became even more so after some cancer scares.

After the killing of Mr. Floyd, she said she immediately felt compelled to post a message to employees on WW's internal social-media network about racism and Black Lives Matter. "I'm prepared for someone to be offended by this," she wrote in a post she later put on LinkedIn. "I'm lucky that my leader is not one of them," referring to WW CEO Mindy Grossman.

Ms. Seymour said she still finds herself accommodating bias in daily life. She instinctively raises her merchandise high in the air when she goes shopping in a department store so that store workers know she's not stealing.

She said she believes most black executives in her generation have succeeded in a similar way, going out of their way to make white people feel comfortable around them. Many in her cohort feel they can only tell the truth after reaching a certain level, she said, but younger employees aren't waiting for that moment. "Now more people are getting there and getting there faster, willing to risk the comfort of their positions for the power of their convictions," she said.

After recently becoming a partner in PricewaterhouseCoopers LLP's deals team, Crystal Wright, 38, said she has allowed herself to become more vulnerable with co-workers by expressing the fear she feels for her husband and what it would mean for her family -- she has a 16-month-old son -- if she were to lose him.

She said the U.S. chairman of the firm, Tim Ryan, has created a platform to talk openly about the topic of race, and white employees are sharing their stories, too. One of her white co-workers recently told her that he's trying to talk with his children about race and how interactions with the police might be different for people of color.

She said she hopes employees will also become more candid about their experiences within their own companies. "An issue with the police is one story, but it's another thing to listen to someone tell a story that 'I feel like I didn't get a promotion here because I was discriminated against,' " she said. "If we want change within corporate America, those conversations are pivotal."

--David Benoit and Jennifer Maloney contributed to this article.

Write to Khadeeja Safdar at khadeeja.safdar@wsj.com and Keach Hagey at keach.hagey@wsj.com