WASHINGTON — Hundreds of Black Lives Matter activists, black and white, marched outside the Minnesota State Fair this weekend, hoping to bring attention to the deaths of African-Americans at the hands of police.

Inside the fair, a booth also represented the group, with T-shirts bearing the slogans “Black Lives Matter” and “All Lives Matter” for sale. Todd Gramenz, who reserved the booth, chatted with fairgoers while the other protesters were kept outside.

The competing activities in Minnesota underscore the challenge that Black Lives Matter faces as it evolves from social media hashtag to full-blown movement. Its fluid, organic nature and loosely organized structure generate confusion about exactly who is in charge, who can legitimately speak for the group and its long-term goals.

Tracing its roots back to the fatal 2012 shooting of 17-year-old Trayvon Martin in Florida, the Black Lives Matter movement gained national ground after 18-year-old Michael Brown was shot and killed by a white police officer in Ferguson, Missouri.

Since then, deaths of other unarmed black men at the hands of law enforcement officers have inspired protests under the “Black Lives Matter” moniker.

Some are affiliated with the original Black Lives Matter network founded by Opal Tometi, Patrisse Cullors and Alicia Garza and their allies. But some are not, even though they use the slogan.

Garza said in an email interview that her organization — which has 26 chapters, stretching to Ghana and Canada — doesn’t try to control who uses the name.

“Anytime someone identifies with a movement to make black lives matter in this country and around the world, that’s a good thing,” she said.

Said Tamika Mallory, part of the allied-Justice League NYC: “There is no way to lead the entire Black Lives Matter movement because it is multifaceted.”

Some similarly loosely organized social movements, like Occupy Wall Street and the Tea Party, evolved beyond their grassroots beginnings, while some died on the vine.