New York (CNN) Americans are being killed. Murdered not for what they have done or being in the wrong place at the wrong time.

Slaughtered again and again because, whether Jewish, or black, or simply not "pure" white, they are seen as a pestilence to be purged.

Their murderers are followers of a vile and hateful ideology that meets the FBI definition of terrorism . But some top current and former law enforcement officials say that they are not treated as terrorists, because they are American, and they are white.

But amid the rising number of deadly white supremacist attacks, the officials say that must change. White supremacy must be called terrorism and tackled with the same vigor as ISIS and al Qaeda.

Manhattan District Attorney Cy Vance came to that realization while investigating the homicide of a black man in the center of New York City.

66-year-old Timothy Caughman was walking alone in Midtown Manhattan collecting cans to recycle when a man approached from behind. That man plunged a sword through Caughman's chest.

Caughman uttered his last words as he turned toward his killer: "Why are you doing this?"

The man continued to stab him. Caughman bled to death.

The answer to Caughman's question would soon become clear. His killer, James Jackson, had come to New York from Maryland with a plan to start a race war.

This was more than a murder, Vance decided. It was more than a hate crime. It was the targeted killing of a black man with the aspiration of dividing the races to keep killing each other, ending in the death of every black person in the United States and around the world, according to Jackson's manifesto, Vance said.

The case was a seminal one for the district attorney's office and for New York state, where it was the first domestic terrorism conviction of its kind. Vance hopes it sends a message.

"I think we needed to call it what it was," he told CNN.

"This was an act of terrorism," Vance explained. "This exists in our country and it happened here."

Manhattan District Attorney Cy Vance charged a white supremacist with a domestic terrorism charge.

It's just that Americans are having a hard time admitting it, he said. It is much easier, Vance continued, for people to call someone a terrorist when they have a different skin color, or don't speak English. But if you are trying to spread fear and wipe out a specific group of people, like Jackson was, then you must call them terrorist, he said. Calling someone a terrorist not only raises the profile of the case but can yield additional charges, and higher sentences.

On the face of it, the killing of Caughman fits into the FBI's category of "domestic terrorism": Perpetrated by individuals and/or groups inspired by or associated with primarily US-based movements that espouse extremist ideologies of a political, religious, social, racial, or environmental nature.

Caughman's murder may not have sparked a national outcry. But it is part of a very public and growing, deadly trend of domestic terror attacks committed largely by white men. From the Charleston church massacre through the killing of a protester in Charlottesville and the shootings at synagogues in Pittsburgh and Poway, far-right extremists are responsible for -- or suspected of - most of the ideological killings in America in the last 10 years , according to data from the Anti-Defamation League (ADL), which tracks extremist activity.

James Fields plowed into protestors at the Charlottesville rally.

White supremacist murders in the US "more than doubled in 2017," with far-right extremist groups and white supremacists "responsible for 59% of all extremist-related fatalities in the US in 2017," ADL's audit shows. They were responsible for 20% of these fatalities the year before.

Depending on who you ask, white supremacist terrorism is either not a problem, or the biggest threat to American democracy in years, but one that's often ignored.

President Donald Trump has said he does not regard white nationalism as a rising global threat.

When asked in the aftermath of the New Zealand mosque massacres if he saw a worrying rise in white supremacy movements around the world, he replied: "I don't really. I think it's a small group of people that have very, very serious problems, I guess."

Intelligence and law enforcement officials under Trump maintain they work to keep up with all threats, though they often don't single out white supremacism publicly, instead referring to domestic terror as a whole. A Department of Homeland Security (DHS) official said the department has a Center for Faith and Opportunity that works with houses of worship to prepare for acts of terrorism and there are other programs that religious and other communities can use to help protect against hate crimes.

But it's still a mistake not to call out white supremacy, according to the former head of the Countering Violent Extremism Task Force at DHS, George Selim.

"If the same number of Americans had been killed at the hands of an individual that was inspired or directed by a foreign terrorist organization, you can bet this Congress and any administration, irrespective of political party would be reacting much differently," he said.

DHS declined to answer specific questions on this story.

Selim will take his arguments to Congress on Wednesday, when he testifies in front of the House Oversight's Subcommittee on Civil Rights and Civil Liberties. The hearing is titled "Confronting white supremacy: The consequences of inaction."

President Obama is briefed by George Selim, second from left, ahead of a White House Summit on Countering Violent Extremism.

It's a subject Selim feels he knows too well. During the Bush and Obama administrations, he was often in the room -- whether the Situation Room or the Oval Office -- when key decisions were made about tackling extremism at home.

And as they saw the threat of white supremacists grow, Selim said he worked with colleagues on federal programs, specifically at DHS, that aimed to address and intervene during the radicalization process.

They "were on the cusp" of creating a system to do just that, he said. With bipartisan support, key puzzle pieces were being put in place in the final months of the Obama administration, he said.

And then Trump took office. Selim said during the first seven months of the administration there was a "decimation of the people, resources and prioritization" of those key programs and infrastructure that was aimed at working with law enforcement, counter-messaging, community resilience and engagement and outreach.

He became so frustrated he quit. He saw that the domestic terrorist acts killing Americans were predominantly perpetrated by those with views tied to white nationalism or supremacy, but the new administration had different priorities.

"It's a significant enough [threat] that the federal government needs to devote significantly more people, money and time to both assess and ultimately mitigate," argued Selim, who now leads the education, law enforcement and community security programs for the ADL and oversees the work of the group's Center on Extremism.

'The new normal': Radicalized white men

In some ways, the precursors to the racist murders mirror those before foreign terrorist attacks. The radicalization, specifically online, is similar to those who pledge allegiance to ISIS or al Qaeda, experts say. One of the noticeable differences is these extremists are white.

Timothy Caughman's murderer focused on his hatred for African American men before traveling to New York City and killing him.

White supremacist James Jackson was sentence to life in prison for the terror attack on a black man.

In the three weeks before Jackson attacked, he spent huge amounts of his days and nights online studying Nazism and extremism until he was apparently pushed over the edge, Vance said. Interracial dating was an "insurmountable problem," in his mind. He read obsessively about Dylann Roof, who killed nine black worshippers in Charleston in 2015, Vance said.

"The racial world war starts today," Jackson wrote in his manifesto, according to Vance. "Negroes are obviously first on the list for extermination."

The gunman in Charleston and the Pittsburgh and Poway suspects all engaged in hateful speech online before taking their rage and turning it into deadly action.

A woman mourns at a memorial outside the Tree of Life synagogue in Pittsburgh.

Officials acknowledge this pattern and it's one reason that Selim believes something can be done to stop these people who are sometimes categorized as untraceable "lone wolves."

Selim also said that, too often, there seems to be a reluctance to name white men as possibly dangerous. And that itself is dangerous because white supremacists and nationalists are a "real and persistent threat," he said.

"As I look forward in the next five to 10 or more years, we need to acclimate ourselves to the new normal, which is increased incidents of domestic extremism, domestic terrorism, anti-Semitism, and all acts of bigotry or Islamophobia, xenophobia that target ethnic and religious minority groups," he said. "Once we understand that that is very likely the new normal, then we can put in place some of the strong infrastructure related to counterterrorism and community resilience that we've already built up and focus it on these new threats that we know we're going to be facing."

With the administration prioritizing other matters, Selim is hoping legislators will hold them accountable and encourage action beyond denunciations of extremist atrocities.

He insists some of the attacks that cost lives are preventable. He advocates for cooperation between law enforcement, social media companies, community leaders and groups like the ADL. And he believes that the initiative he led at the Department of Homeland Security would have borne fruit if funding had been continued.

"The setback won't be able to be measured here and now," Selim said. "I can't tell you that funding of these programs would have prevented Pittsburgh or Poway, but I can say in good conscience that we sure would have stood a better chance at preventing or intervening in incidents like this had funding for these programs continued."

Sending a powerful message

If Selim is hoping Congress will take steps on the identification of dangerous white supremacists, Manhattan DA Vance is hoping the same people will take action on what can be done with suspects once identified.

Many states do not have terrorism laws on the books or prosecute cases the way he did with the murder of Caughman, who called himself a can and bottle recycler and autograph collector on his Twitter account, where he posted a photo of himself waiting to vote in the 2016 election.

Standing on line waiting to vote I love america󾓦󾓦󾓦 pic.twitter.com/jVAeLXtUAq — timothy caughman (@timrock715) November 8, 2016

But Vance stands by his decision. "It really is no different from him to come up and to seek out to kill black men than a radical Islamist to come to a place to seek out, to kill, men and women who weren't of their faith," Vance said.

And calling it terrorism and getting a life sentence can send a powerful message that white nationalism will not be normalized in New York, Vance said.

He wrote a letter to the House Appropriations Committee urging them to increase federal law enforcement funding. "We can no longer sleep on the danger posed by this country's increasing number of white nationalists. And we cannot continue to treat this type of hate-fueled violence as a lesser form of terrorism, lest we risk normalizing this repulsive behavior and missing opportunities to prevent future attacks."

Assistant Director for Counterterrorism Michael McGarrity testified that the FBI has 850 open domestic terrorism investigations, 40% of which are cases of racially motivated violent extremism.

FBI Assistant Director Michael McGarrity testified to the House Committee on Homeland Security last week that the bureau is doing its part to tackle the issue on a federal level. He shared that the Trump administration has added domestic terrorism to its national security strategy, a first for the country.

"We're highlighting that there is a domestic terrorism threat that is persistent," McGarrity said. "We don't differentiate between a domestic terrorism attack we're trying to stop or an international terrorism attack. It's a terrorism attack we're looking to stop," he said.

But to Selim, the lack of specificity was troubling. He wanted to hear officials say white supremacists. White terror. White nationalist terrorism. To voice what is an unsettling truth -- today's terrorism in the US is most often perpetrated by white Americans who look more like the Founding Fathers than foreign-born jihadis.

Double standards

Outside of perception, the law itself also creates a double standard.

Jeff Sessions promised a tough response from federal authorities after the Charlottesville attack.

Then-Attorney General Jeff Sessions initially told ABC's "Good Morning America" that the killing of Heather Heyer in Charlottesville met the "definition of domestic terrorism." But James Fields, who drove a car into counter protesters at high speed, wasn't charged with being a terrorist as there is no single crime of domestic terrorism.

Even similar attacks are handled differently depending on the perpetrator in the US. Sayfullo Saipov allegedly rammed a truck along a New York City bike path, killing eight people, three months after Fields' attack.

But Saipov, unlike Fields, was able to be charged with a federal terror offense because of one simple difference -- his alleged allegiance to the foreign ISIS organization.

Dylann Roof, left, and James Fields, center, were not charged with terrorism. James Jackson, right, was under New York state law.

Another case is the Coast Guard lieutenant currently accused of plotting a domestic terror attack. Prosecutors say he planned to conduct a mass killing of prominent Democratic politicians and members of the news media, including CNN. But without a law saying domestic terrorism is a crime, he can only be charged with lesser offences.

"To illustrate how ridiculous the current situation is, when I was in the FBI investigating people inspired by international terrorist groups like ISIS and al Qaeda, the mere association with those groups was enough to land someone behind bars," said Josh Campbell, CNN law enforcement analyst and former FBI special agent. "Not so with domestic terrorism. Even if someone is politically motivated to cause violence due to their right- or left-wing extremist views, that's not enough to get them off the street. Opponents to such a law claim it might infringe on free speech. The issue appears to be a political third rail that few in Congress actually want to touch."

Campbell said that the FBI Agents Association, a private organization that represents the bureau's approximately 13,000 special agents, has been very vocal about the need for new legislation that would equip law enforcement with the tools needed to stop these threats.

(2/3) "The FBIAA urges Congress and the White House to ensure that federal law enforcement has the tools to track, investigate, and punish domestic terrorists. This means amending the United States Code to include a penalty for domestic terrorism regardless of target or weapon." — FBI Agents Association (@FBIAgentsAssoc) October 24, 2018

A 'scary' silence

In last week's House hearing, members asked the assembled law enforcement chiefs about the online activity of the alleged Poway shooter, who appears to have posted a manifesto on the 8chan site and been cheered on there, as have white supremacist attackers before him.

Rep. Mike Rogers, the ranking Republican member of the committee, asked intelligence and law enforcement experts from the FBI, Justice Department and DHS how the US can tackle the issue, seeking advice to guide possible legislation.

"Do you have any recommendations about what can be done to address the violent hate speech and incitement of violence found on fringe sites like 8chan and Gab, and that's for any of you," he asked.

He was met with silence.

"Y'all don't have any suggestions for us?" responded the Alabama congressman. "That's scary. We can't make policy without good advisement."

The officials then explained the difficulties in monitoring the forums and balancing free speech. And DHS says they have developed robust partnerships with the tech sector.

But at the root of it all, again, is there's no domestic terrorism statute.

Which is another reason Vance wrote his letter. "I think it's a big problem and we focused so much on Islamic radicalism since 2000, since 9/11, that I think perhaps we've taken our eye off the ball of what is an equally large problem -- and that is those who are being radicalized in our midst," Vance told CNN.

He admits he was himself late to see the issue.

"If the Manhattan district attorney -- I'll profess having more ignorance than I should have had -- but if I'm not paying attention to it, then, probably a lot of people aren't paying attention to it enough also," he said.

He's now set his office on a new course, and hopes more will follow, from the federal level on down, however painful it may be.

"I think as, as white Americans, we may not be as readily willing to identify this group of terrorists that are like us," he said. "And I think that's perhaps a little bit of human nature it's easier to identify the enemy as someone who doesn't look like you or doesn't speak the language, but when it is your neighbor and like people you know, then it's, it's harder to, it's hard to call that out ... and call it terrorism."