If you watched the disgraceful invasion of the U.S. Capitol and the horrific destruction that took place on Jan. 6, you observed a legion of limited-intelligence, low-life louts.

But you’d be mistaken if that’s all you thought of the Trump-incited mob. Those people could not have infiltrated the Capitol without the help of some “law enforcement” officers in the Capitol. Somebody had to open locked doors and side entrances. Somebody had to tell the invaders where certain Congressional offices were. And too many Capitol Police officers took selfies with the invaders and treated them with extreme courtesy, going so far as to open doors for them and even walk them down steps.

Why were the Capitol Police so woefully unprepared for the throngs of people who had been communicating by internet since an unhinged 45th president invited them to the Capitol weeks ago on Dec.18?

Contrast that under preparation to the army of thousands that Black Lives Matter activists faced this summer. The contrast was stark.

After the invasion passed, many speculated about the inside nature of this invasion. Some of the Capitol Police seemed to feel quite comfortable, even chummy, with the invaders.

Why shouldn’t they be? Some members of the mob might be their cousins. There is a historical relationship between so-called law enforcement and white supremacy, so it is easy to believe that the Capitol invaders may have had help from the inside. We could go into history to explore the founding of the Ku Klux Klan and its purpose to terrorize and otherwise oppress Black people. We could explore how many Klan members were also “law enforcement” officers. In 1898 in Wilmington, N.C., we could consider how sheriffs deputized more than 200 racist civilians to force Black people to turn their property over to them and leave town. But if we had to go back to the late 19th and early 20th century, that would allow us to talk about how much our nation has changed instead of focusing on the intransigence of the myth of white supremacy.

Michael German of the Washington, D.C.-based Brennan Center for Justice released a report in the fall that explored the law enforcement and white supremacists connection. Titled “Hidden in Plain Sight: Racism, White Supremacy and Far-Right Militancy in Law Enforcement,” the report

is a comprehensive exploration of racism in law enforcement. It documents ties between law enforcement and “violent racist and militant groups.”

It says that the FBI has not appropriately responded to the threat that is posed from this connection. But, according to Mr. German, “Despite the FBI’s acknowledgement of the links between law enforcement and these suspected terrorists, the Justice Department has no national strategy designed to identify white supremacist police officers or to protect the safety and civil rights of the communities they patrol.”

The Brennan report appropriately notes that “only a tiny percentage of law enforcement officials are likely to be active members of white supremacist groups.” But even a 10th of a percent is enough. It only takes one armed white supremacist to aid and abet the terrorists who stormed the U.S. Capitol. It only takes one to unlock a door. It only takes one to turn the other way as terrorists bring weapons into the Capitol.

The Brennan report documents several cases of white supremacist law enforcement “officers” who collect Klan paraphernalia, participate in racist social media posts, rant rhetoric on their government-issued radios and more. Few face any consequences. Some have supervisors or police chiefs who look the other way. Others have police union backing and often claim their First Amendment free speech rights. How does their racism affect their ability to enforce the law? Ask Breonna Taylor or George Floyd or Tamir Rice or Sandra Bland.

Why have federal, state and local law enforcement failed to tackle evidence of virulent racism among police officers? No wonder there is so little trust between law enforcement and the Black community. If there were an active attempt to combat law enforcement racism, it would be almost unthinkable that anyone could see the Trump insurrection as an inside job. But there has been no such attempt. Perhaps because too many police officers are either outright racists or have sympathy with these racists.

Was there an inside job with this Trump insurrection? It is likely, and I look forward to the inevitable investigation and its results.

The writer is an economist, educator and author.