A protest leader in Ferguson, Missouri, could face up to four years in prison after being charged with a felony for allegedly kicking a vehicle as it ploughed through a line of peaceful demonstrators who were blocking a highway.

Brittany Ferrell was accused of causing damage worth more than $5,000 to the SUV as its driver forced her way through the group, which had gathered on Interstate 70 near Ferguson during events to mark the anniversary of the fatal shooting of Michael Brown, an unarmed black 18-year-old, by a police officer.

Ferrell, 26, was charged with first-degree property damage, which is a class D felony in Missouri. She was also charged with trespassing and disturbing the peace, according to Bob McCulloch, the prosecuting attorney for St Louis County, who oversaw the grand jury inquiry into Brown’s death. Ferrell was released on a $10,000 bond on Wednesday.

Ferrell’s wife, Alexis Templeton, was charged with misdemeanour assault for allegedly punching the driver through her vehicle’s window, and misdemeanour charges similar to Ferrell’s for alleged trespass and disturbing the peace. Templeton, 21, has also been released.

The charges prompted a furious reaction among the wider Black Lives Matter protest movement. Brittany Packnett, an activist who sat on Barack Obama’s White House taskforce on police reform, said several demonstrators were struck by the vehicle.

Oath Keepers militiamen ‘on patrol’ in Ferguson. Link to video

“Feet don’t cause $5K worth of damage to cars,” Packnett said on Twitter. “McCulloch meant ‘drive over’, not past. They were almost hit.”

Soon after being released on Wednesday Templeton was defiant. “I’m not worried & y’all shouldn’t be either,” she said on Twitter. “We gon get free whether they like it or not!” She urged St Louis county police department to “quit lying”.

The two women are the co-founders of Millennial Activists United, an activist group that grew out of the demonstrations in Ferguson last summer. They married in December 2014 after months of protesting against the deaths of Brown and other people killed by police.

They were arrested the day after the rush-hour highway shutdown, which took place on a “Moral Monday” of civil disobedience, when they went to inquire about dozens of other people arrested during the protest action.

The couple’s attorney, Aaron Banks, did not immediately respond to a request for comment.

In a statement McCulloch alleged: “The charges stem from the efforts of the defendants to block traffic on Interstate 70. Templeton is accused of punching the victim as our victim attempted to drive past the defendant. The victim suffered an eye injury as a result. Ferrell kicked the victim’s car as she passed causing nearly $5,000 in damage.”