More than three weeks since the death of George Floyd, anti-racism protests are continuing across the US.
While in many cases peaceful, the protests have also featured scenes of police brutality, looting and violence.
Politicians, law enforcement and commentators on the left and right have accused a number of fringe groups of encouraging and participating in acts of violence.
BBC News has been examining these groups on social media platforms.
This relatively new anti-government subculture is perhaps the most dangerous of the bunch. Steven Carrillo, a 32-year-old US Air Force sergeant from California, has been charged with the murder of two officers during the George Floyd protests, one in Oakland and another in Santa Cruz.
Before being arrested, he wrote in his own blood the terms “boog” and “I became unreasonable” on a car. Both terms are commonly used by the movement.
Rooted in a bulletin board dedicated to firearms on 4chan – called the /k/ board – Boogaloo Bois is a loose, leaderless movement.
The group’s name is a reference to a poorly-reviewed 1984 film, Breakin’ 2: Electric Boogaloo. The phrase “Electric Boogaloo” has since become an online meme meaning a low-quality sequel.
But Boogaloo Bois use it to refer to armed conflict with authorities, something akin to a second US Civil War.
Relatively small on 4chan in its early days, the movement has since considerably grown in size, notably helped by dozens of Facebook groups and pages with tens of thousands of members and followers. In order to evade Facebook restrictions on the word “Boogaloo”, alternate terms like “Big Igloo”, “Boog” and “Big Luau” are also frequently used.
Like other online movements born out of 4chan, Boogaloo Bois are steeped in the vernacular of internet memes and in-jokes.
Some in the movement refer to themselves as “boojahideen”, a parody of the term “mujahideen” which is frequently used to refer to radical Islamist militants.
Followers have a variety of views and levels of seriousness towards the movement, but most could be described as extreme libertarians and sign up to two fundamental beliefs: A desire for an armed overthrow of the government, and an unwavering commitment to gun ownership.
Boogaloo Bois were overwhelmingly opposed to coronavirus lockdowns, which they saw as an alarming sign of tyranny. When anti-lockdown gatherings were held in several states in April and May, some armed members of the Boogaloo movement were seen in the rallies, often wearing Hawaiian shirts – a tongue-in-cheek reference to Hawaiian luau celebrations.
Black Lives Matter protests have caused a divide in the group. While many support the protests and are anti-police, some in the movement’s more radical circles are conflicted.
Facebook groups and pages post footage of armed members in Hawaiian shirts attending the protests carrying Boogaloo flags, claiming they are there to protect the protesters from police. Some even suggest that the demonstrations might trigger the “Boogaloo” that they’ve been waiting for.
Videos and hashtags sympathetic to the group have also appeared on TikTok in recent weeks. They are often posted by young men with firearms who call for an uprising. One video features captions such as “becoming more and more willing to die” and “cops showing at your door will be targeted first”.
Some members are capitalising on the protests to engage in acts of violence against authorities. Three Boogaloo members were charged with terrorism offences in Nevada this month for alleged attempts to “spark violence” in protests.
Facebook has since limited the reach of Boogaloo-themed groups and pages. Several have been removed – or “got Zucced”, as members call it – in the last few days.
Antifa, short for “anti-fascist”, is a loose affiliation of mostly far-left activists.
They include anarchists, but also communists and a few social democrats. What sets them apart is their willingness to use violence – they say, in self-defence or to defend their communities.
The movement, which at one point almost entirely disappeared in the US, saw a surge of interest after the election of Donald Trump. They routinely clash with the far right.
During the recent protests, there’s some evidence that they’ve been involved property damage and looting. Authorities in Texas, for instance, say three alleged looters in Austin were antifa affiliates.
But right-wing activists and President Donald Trump have made much bigger claims – that they are the driving force behind the violence.
While US presidents can designate individuals or groups as foreign terrorists, legal experts have questioned whether Mr Trump has the authority to label antifa a “domestic terrorist organisation”.
There’s little evidence for the sweeping claims. Antifa activists are relatively rare – their numbers are tiny compared to the size of the US protests.
Founded in 2016 by Canadian-British right-wing activist Gavin McInnes, the Proud Boys is a far-right, anti-immigrant, all-male group with a history of street violence against its left-wing opponents, notably antifa.
The group’s name is a reference to a song from the Disney film Aladdin. Members often wear black and yellow Fred Perry polo shirts along with red “Make America Great Again” hats.
A member must declare that he is “a Western chauvinist who refuses to apologise for creating the modern world”.
The Proud Boys and affiliated groups have faced off against antifa in a number of violent street rallies in the last two years, most notably in Oregon, Washington and New York. Two members were jailed last year for beating up antifa activists in New York.
The Southern Poverty Law Center (SPLC), a prominent civil rights group, describes the Proud Boys as a hate group.
Although Mr McInnes quit the group in November 2018, he filed a lawsuit against the SPLC three months later. Enrique Tarrio is the group’s current chairman.
Proud Boys members are vehemently opposed to BLM protests. Describing attempts to bring down statues of Confederate leaders as a left-wing plot to “destroy American history”, members have been seen “guarding” statues of historical figures in a number of states.
Following the establishment of the Capitol Hill Autonomous Zone, a police-free district in Seattle, Proud Boys members – some armed – turned up to confront what they called “authoritarian behaviour” by the protesters.
Photos and videos of clashes between the group and antifa members near the zone have gone viral.
Facebook, Instagram, Twitter and YouTube have all banned the group from their platforms. But accounts associated with the movement have popped up again during the protests. This week, 358 Facebook accounts and 172 Instagram accounts tied to Proud Boys were removed.