In 68 hours this week, America changed.

The country, simmering under the heat of a chaotic presidential race and the tension of increasingly volatile race relations, is reeling after a sniper in Dallas struck down five white police officers and police in Louisiana and Minnesota killed two black men — all in 68 hours.

The Bay Area is used to tumult, but what grips the country now is shaking us all: Where do we go from here?

James Taylor fears the answer. “This has put us on the precipice … of more chaos and a return to the violence we saw in the 1960s,” said Taylor, who is the director of the African-American studies program at the University of San Francisco.

Now, Americans find themselves grappling with a wave of racial animosity not seen in decades.

Leaders everywhere, from President Barack Obama to Dallas police Chief David Brown, condemned the violence Friday and urged calm. Vigils spread and protests began anew, including one on San Francisco’s Market Street. And while there were small attempts at reconciliation, including a black teenager delivering doughnuts to an Oakland police headquarters that had been splattered with protesters’ graffiti, many scholars fear the worst is far from over.

“It was just a matter of time,” said Harry Edwards, and African-American sociology professor emeritus at UC Berkeley and a well-known civil rights activist. “Anybody who thinks Dallas is the last incident of that kind doesn’t understand how systems break down.”

With video technology and social media, he and others say, suddenly every act of police violence has become national news, fueling the anger and distrust between black citizens and police.

“When we see that run in a loop,” Edwards said, “we should not be surprised when all of a sudden we get snipers on buildings in Dallas.”

There have been numerous video recordings of white officers shooting to death black men since 2009, when BART police officer Johannes Mehserle shot Oscar Grant, an unarmed Hayward man, in the back, an event that sparked weeks of protests in downtown Oakland.

But few have matched the gut-wrenching intensity this week of police killing a Louisiana man as he lay on the ground and a Minnesota woman livestreaming the final moments of her boyfriend’s life after an officer shot him during a traffic stop.

The next night, as protesters marched in Dallas, police say 25-year-old Micah Johnson sought vengeance on officers, killing five and wounding seven more.

Cat Brooks, who has organized Black Lives Matter protests across the Bay Area, said the violence marked a fork in the road for race relations in the Bay Area and beyond.

“I think what is happening is a scab has been ripped off the wound too soon, and all this stuff is gushing out,” she said. “Either we’re going to be able to have honest conversations that create just societies, or we’re going to continue down this path that could very likely lead to more explicit racial violence.”

The notion of more racial violence seemed unthinkable eight years ago as Obama began his presidency. Instead tensions have boiled over and the political discourse has become cruder, with Donald Trump belittling illegal immigrants and calling for a ban on Muslims visiting the country.

“We thought we were OK, we thought we were kind of post-racial as a society,” said Na’ilah Nasir, the vice chancellor for equity and inclusion at UC Berkeley. “To be faced by this disjunction is really jarring for people.”

The embers of racial animus burned in Sacramento last month when white nationalists and leftist protesters waged street fights. And racial tension filled downtown San Jose in May when several protesters, most of whom were Latino, targeted Trump supporters as they left a rally where the presumptive Republican nominee electrified his audience by saying he would make Mexico pay for a giant border wall.

“People were screaming at all of us as we were trying to find our way out of there,” said Corrin Rankin, a Trump supporter from Redwood City. “I never experienced anything like that in my life.”

Rankin, who is black, said she understood the “anger and frustration” felt by Black Lives Matter protesters, but disagreed with their tactics, and feared that her former husband, a police officer, was more at risk now than ever before.

“It’s creating hostility for everyone,” she said. “It’s making citizens more hostile to police officers and officers more hostile to citizens.”

Former Oakland police Chief Howard Jordan, who led the department in 2009 when a gunman fatally shot four officers, said the protest movement that emerged after Grant’s death has made it harder for police to protect and serve.

“We’re being demonized,” he said. “I think when people stop demonizing police and start respecting them you can have a legitimate conversation about what it would take to rebuild trust and ensure that officers are doing their jobs in a professional manner,” he said.

Jordan said black officers, such as himself, have had an extra burden to carry. “People call you an Uncle Tom because they think if you’re black you shouldn’t arrest other black people,” he said. “You can’t take that stuff personally. And the people who do don’t last very long.”

Not everyone sees doom and gloom for race relations. David Hilliard, a founding member of the Black Panther Party, said police treat minority communities far better than they did before the Panthers formed.

“You’d have to be blind or totally out of your mind not to see the positive changes since the Civil Rights movement,” he said. “You’ve got a black president, and you’ve got a lot more black and minority officers.”

Eugene O’Donnell, a former New York City officer and a criminal justice professor at John Jay College of Criminal Justice in New York, said police-community relations aren’t nearly as bad as they are being portrayed, but they could be sabotaged by demagogues hogging the cable news airwaves.

“You have extremists taking over the conversation on both sides of the political spectrum,” he said. “The crazy people who are race obsessed are driving the conversation. That’s not where people are in real life, but you can drive them there.”

Jaren Stewart, a 19-year-old college student, and his friend Zane Castillo tried Friday to help defuse tensions by bringing three boxes of doughnuts to Oakland police headquarters.

“As an African-American, I feel the pain of the men who were killed by police,” Stewart said, “but I couldn’t imagine if five of my rugby teammates died in one night. Being able to step aside from my pain and acknowledge someone else’s, that is the first step to how we are going to fix this issue.”

Contact Matthew Artz at 510-208-6435. Follow him at Twitter.com/Matthew_Artz.