Late one night a few weeks after George Floyd was killed by Minneapolis police, a loud knocking came on Jaquita Morris' door, and two of her sons tumbled into the family's North Side home.

But her annoyance turned to shock, then anger when the boys, 19 and 14, told her they were waiting for a bus to their older brother's house when they saw two white men wearing all-white "KKK gear" appear from behind a bush and start running after the terrified teenagers before they reached safety.

As south Minneapolis was enveloped in protests, riots and looting in the wake of Floyd's May 25 death, authorities received dozens of similar reports of racial attacks, harassment and vandalism, many of which were centered on the predominantly Black North Side. There was confusion about whether outside influence was present in the days after Floyd's death, when state officials gave conflicting accounts of whether the suspected agitators came from the ranks of white supremacists exploiting the rage over Floyd's death, or left-wing anarchists bent on turning the anger toward their ends of discrediting the police.

Local authorities have opened investigations into several racially motivated incidents, like the case of the "Umbrella Man," who police believe has ties to the Hell's Angels and Aryan Cowboy Brotherhood motorcycle gangs and was seeking to incite racial tension when he was recorded smashing out the windows of an auto-parts store that later went up in flames. The case could wind up in federal jurisdiction.

Minneapolis Police Department spokesman John Elder said no statistics on race-related offenses were kept, but investigators had sorted through reported crimes and incidents after Floyd's death, looking for patterns or trends.

"There were no such patterns," Elder said, while adding that some cases remain open and under investigation. Of the dozens of people charged so far with crimes related to the riots, none have been publicly linked to white nationalist groups.

Monitored movements

The threat posed by far-right, neo-Nazi and white nationalist groups has captured headlines of late, in light of protests that turned deadly in Kenosha, Wis., after the police shooting of Jacob Blake and in Portland, Ore., where protests have been ongoing since Floyd's death.

Minneapolis Police Chief Medaria Arradondo said his department received information from federal law enforcement partners suggesting that the post-Floyd unrest might draw groups "with the sole purpose of harming and committing violence on African Americans."

"We had certainly heard that there may be extremist groups up here to cause harm to our African American community," Arradondo said in a recent interview.

Similar reports surfaced, he said, during protests in 2015 of another Black man killed in police custody, Jamar Clark, at which Allen Scarsella, deemed a white supremacist by prosecutors, shot and wounded five protesters. He is serving a 15-year prison sentence for first-degree assault.

According to a trove of leaked law enforcement documents dubbed "Blue Leaks," federal authorities were monitoring the movements of suspected white nationalist groups, as well as left-wing extremist groups, in the weeks after Floyd's death.

A post on a white supremacist channel on the encrypted messaging app Telegram called on followers to fire into protest crowds to start a second Civil War, according to an intelligence memo.

Meanwhile, forums linked to the Base and the Nordic Resistance Movement mentioned targeting critical infrastructure. One post suggested that "the real way any of us benefit [from] this situation is to go after serious infrastructure," while another read: "If the power goes out in any of the affected cities right now on top of what's already happening, you can expect them to really shatter."

Other reports have been debunked, including one suggesting a group of white supremacists had reserved a block of rooms at a Fridley hotel.

At the height of the protests, state Public Safety Commissioner John Harrington said he was dubious about reports of "crazy stuff about the Klan marching down the street," saying that "some of it looks like it is deliberately being planted as disinformation." A spokesman said this week that state authorities had received no new information that would suggest otherwise.

Doubly victimized

Minneapolis violence prevention director Sasha Cotton said that cities like Baltimore and Ferguson, Mo., also saw an increase in racist and far-right activity after controversial police killings, saying that such groups "operate best in the chaos."

"While it may not have been able to be substantiated by police data or other accounts," she said, such incidents can add to the emotional pain and psychological distress many African Americans already felt at watching Floyd die on video.

The Anti-Defamation League, which documents and reports on bigotry and hate movements, reported that white supremacists were sent to "monitor" post-Floyd protests in Florida, Arizona and South Dakota. But it also warned that pinning blame for the unrest on outside groups "diminished" protesters' message that communities were so frustrated and angry by police killings that they would rise up and revolt.

Many Black residents felt doubly victimized, first by the trauma of watching Floyd's dying under the knee of a since-fired officer, and then the unexplained racial incidents that followed, according to Nekima Levy Armstrong, a civil rights attorney and one-time mayoral candidate.

"Too often, the concerns of Black people are being ignored — this is how the Minneapolis police were allowed to get out of control over so many years," she said.

Morris, the mother of the two teenagers, called police immediately after her sons came inside the house the night of June 15, several weeks after Floyd's death. She said she wasn't sure that the officers took her concerns seriously — asking over and over again whether the boys were sure of what they saw — until she got a call from Arradondo the next day to promise a "thorough report." The same two cops from the night before showed up, and she gave them an earful.

"We call the people who are put in place to protect us and you question what my boys saw," she said.

A police report of the incident was not immediately available.

Also not long after Floyd's death, Jennifer White recalled seeing suspicious-looking white men driving around the North Side in vehicles with no license plates. One night, one of them shot at her and members of the Freedom Riders, an armed civilian patrol group that was formed to guard Black-owned businesses and churches during the riots.

Fearing the shooters would return, she contacted Arradondo, who came to the restaurant they were guarding at Broadway and Emerson with his chief of staff, Art Knight. Shortly afterward, a volley of rifle rounds rang out nearby, sending some several ducking inside for cover, as Arradondo and Knight drew their service weapons and went to investigate.

"It's not really like folks are carrying membership cards or wearing hoods or things like that to easily identify themselves as being white nationalists or white supremacists or extremists," said White, a public safety aide for Mayor Jacob Frey. "It's almost like racism: when you're experiencing biased behavior or racist behavior ­— there aren't [always] things that indicate it, but you just know it."

Staff writer Stephen Montemayor contributed to this report.

Libor Jany • 612-673-4064 Twitter: @StribJany