Police in Texas have described a gang shootout, which killed nine people, as one of the worst gun fights ever in the city of Waco.
Officers say 192 people face organised crime charges after rival biker groups clashed at a sports bar and grill.
One witness quoted by the Waco Tribune-Herald said the car park of the restaurant resembled "a war zone".
All nine of those killed are thought to be members of the Bandido or Cossack gangs.
There's already at least one documented instance of violence between the two groups.
In November 2013, a 46-year-old from Abilene, who police say was the leader of a West Texas Bandidos chapter, was charged over the stabbings of two members of the Cossacks.
In a 2014 gang threat assessment, the Texas Department of Public Safety classified the Bandidos as a Tier 2 threat, the second highest.
Other groups in that tier included the Bloods, Crips and Aryan Brotherhood of Texas.
So who are those biker gangs?
Slogan: "We are the people your parents warned you about." Members also wear patches with phrases like "Expect No Mercy".
Origins: Formed in Texas in 1966 by Don Chambers, who served as a marine in Vietnam.
Logo: A chubby Mexican bandit, wearing a sombrero hat, pointing a gun and holding a sword. The character's based on an old logo for a brand of tortilla chips.
The gold and red colours were chosen because of Chambers' link to the marines.
Members also wear the "1%er" logo.
The group's Swedish website describes a "One Percenter" as the "one of hundred of us who has given up on society and politicians one-way-laws".
"This is why we may look repulsive (to you). We're saying we don't want to be like you or look like you. So stay out of our face."
The Bandido code: "You don't lie, you don't steal and you don't take a brother's woman."
Location: The group's thought to have 2,400 members in 210 branches. It's concentrated in Texas, but has members in many US states, mainly in the south - making it one of America's biggest gangs.
Members are also active in Canada and Australia, with chapters in 19 other countries including Thailand, Singapore, Germany, Denmark, France. The group also claims to have a small following in the UK.
Initiation: It takes about two years to become a fully patched Bandido. You need to know an existing member and go through a probation period and pay around £350.
Members have to wear patches visible from 150 feet away.
Known criminal activity: The Bandidos have a long and violent history of crime, with the FBI calling them one of the country's five most significant outlaw motorcycle gangs.
Members have been arrested for offences ranging from assault and racketeering, to possession of drugs and illegal weapons and murder.
In 2009, six Canadian members were jailed for life for murdering eight fellow Bandidos in an "internal cleansing" in Ontario.
But one former high ranking leader is quoted as saying that while some members engage in criminal activity, the clubs as a whole don't condone or encourage it.
Edward Winterhalder ("Connecticut Ed") claims 90% of members are "regular working guys with regular jobs and families or older guys living on pensions".
But he concedes Bandidos can be dangerous.
Rivals: The group has had a long-running, violent rivalry with the Hells Angels, among others.
A turf war between the two, lasting from 1993 to 1997, known as the "Great Nordic Biker War" resulted in 11 murders, 74 attempted murders and 96 injuries.
Supporters: The Bandidos also have a number of "support" clubs, used to help with legal and illegal activities. They usually wear reverse colours (gold border with red background).
They also often wear a unique patch known as the "Heart Patch".
Slogan: "We take care of our own."
Origins: Founded three years after the Bandidos in Texas (1969). It's not clear who they were set up by or how they came about, but it's been claimed the group may have sprung out of the Bandidos.
Logo: An angry-looking, muscley Cossack brandishing a sword at his own face with his lizard like tongue out. Their colours are gold and black.
The Cossacks code: The Cossacks claim they traded in the horses used by warriors 400 years ago for motorbikes - although they doubt their members descended from actual Russian Cossacks.
Location: This is a much smaller group than the Bandidos but it's claimed the Cossacks have factions in Australia as well as southern states of America.
Supporters: During the Waco shootout, the Cossacks seem to have been supported by a third biker gang, the Scimitars.