Seventeen-year-old Judy Lai recently encountered two police officers talking to a black man at the Ashmont T stop and found herself worrying that the incident would escalate into violence.

“As a minority, I’m pretty scared,’’ she said. “Right then and there, I started shaking and getting nervous. I started freaking out a little bit. I don’t think that should be happening.’’

After a week that saw the fatal shooting of two black men by police officers in Minnesota and Louisiana and five Dallas police officers killed, allegedly by a black man acting in revenge, young people in Boston were full of anguished stories. They described how their parents counseled them to be wary of gang members — and also now of police officers. How they pleaded with siblings to act in ways that wouldn’t attract police attention. How their brown skin felt, by itself, like enough to provoke suspicion.

Their reactions come against the backdrop of four years of high-profile killings of people of color, starting with Trayvon Martin in Orlando, that have exposed the fraught relationship between the criminal justice system and people of color. The Black Lives Matter movement emerged from unanswered calls for change, and activists have been able to influence the policy positions of the nation’s leaders while informing their racial sensibilities.

Still, the fear among Boston’s youth persists, increasingly palpable as each new video of a violent encounter between police and community goes viral.

Somtoo Ebele, 20, was among a diverse group of young people gathered Friday at the South End Technology Center. She said she watched a video last year that showed a police officer in Texas forcing a bikini-clad 14-year-old girl to the ground and kneeling on her back as he broke up a pool party.

“All I was thinking was: That could be me. I could be dragged by my braids,’’ she said.

But she can’t bring herself to watch the videos that have captured the world’s attention last week, the ones that show Alton Sterling’s and Philando Castile’s bloodied, dying bodies. “I’m tired of seeing black people getting killed. We’re not animals,’’ she said. “That could easily be my little sister.’’

Or, she said, it could be her older brother, whom she texted on Thursday, saying: “Don’t be causing no commotion. Don’t be anywhere with police.’’

His response: “What are you talking about?’’

So she told him: “They will kill you.’’

Then, she said, he got it, responding: “Enough said.’’

Emmanuel Chalumeau, 15, said his mother routinely gives him “the talk’’ — the one black parents give their sons about how to interact with police. But recently, there has been a greater urgency to the conversations. Now, he said, there seems to be a sense that the basic rules — only hang out with friends and be aware of your surroundings — won’t keep him safe anymore.

“All of a sudden, there seems to be no way around them. They will pull you over for no reason,’’ he said.

“I could be drinking water, and I was disturbing something,’’ interrupted Tyla Smart, 18, who said she comes from a military and law enforcement family that has recently become increasingly twitchy about her safety.

“I feel like I look guilty even if I’m just drinking water,’’ Betty Elias, 18, said. “It’s like ‘just act natural’ even if I’m not doing anything.’’

Upon hearing her friend talk, Kiley Blodgett, also 18, had an epiphany about a recent encounter the two had while walking to the South End Technology Center on Columbus Avenue.

“I’m realizing why, when we were walking through the Back Bay on the way here, you saw a police dog and just went the other way,’’ she said.

Gone are the days of looking at police officers as a source of safety, Luisa Perez, 18, said. “You can’t obviously assume that all police are bad, but you have to approach with an air of caution,’’ she said. “It’s kind of like this figurative wall . . . you have to figure out how to proceed.’’

And with each new violent or fatal episode, the wall thickens, but so too does a numbed sense that the unthinkable is now somehow normal, she said.

“Though it’s wrong. It shouldn’t be that way,’’ Perez said.

“It’s like, another one. Really?’’ Elias added.

Frustration follows the news of each new incident — and a lot of talk — but little changes, the teens said.

There are those who have seen this cycle — tragedy followed by protests and fear and inaction — before. And yet, they say, there is something different about this moment.

Mel King, 87, who founded the center where the students studied, described a systematic devaluing of black lives that stretches from the images splayed across television screens to harmful policies implemented within the halls of Congress to the deaths at the hands of people charged with protecting and serving the community.

“We try to deal with these things in isolation, but we can’t,’’ King said. “We’re missing something.’’

Hundreds of men and women have died while in police custody this year, while few officers have been convicted of crimes. More officers were, however, prosecuted for questionable deaths in 2016, according to an accounting by The Washington Post.

The pattern fosters a sense that there is no accountability and creates an air of helplessness that is erupting into anger, said Hubie Jones, the former dean of Boston University’s School of Social Work.

“This is a very different moment than I’ve ever seen, and I was in the middle of two riots in 1967 and 1968,’’ Jones said. “I pick up the morning paper and see the sniper activity that happened in Texas, and you almost feel that we’re at the beginning of a race war.’’

Akilah Johnson can be reached at akilah.johnson@globe.com. Follow her on Twitter @akjohnson1922.