A prominent Black Lives Matter activist and two other protesters arrested last month while demonstrating over the shooting death of Alton Sterling by a white Baton Rouge police officer filed a federal lawsuit Thursday against several local law enforcement agency heads and the city-parish.

DeRay Mckesson, of Baltimore, Maryland, who was active in the Ferguson, Missouri, protests that followed the fatal police shooting of Michael Brown; Gloria La Riva, of San Francisco, California; and Louisianian Kira Marrero are seeking damages for what they call their "unlawful mass arrests" in Baton Rouge. They also allege officers used excessive force.

The suit, which seeks class-action status, was filed against Baton Rouge Police Chief Carl Dabadie Jr., East Baton Rouge Parish Sheriff Sid Gautreaux, Louisiana State Police Superintendent Col. Mike Edmonson, Mayor-President Kip Holden, and the city-parish.

"Defendants employed unconstitutional tactics to disturb, disrupt, infringe upon and criminalize plaintiffs and class members' constitutional rights to freedom of speech and assembly," the suit, filed in U.S. District Court in Baton Rouge, states.

The suit complains that police responded to the protesters in a "militarized and aggressive manner" and pointed their weapons directly at protesters and brandished assault weapons alongside armored vehicles.

Through State Police spokesman Maj. Doug Cain, Edmonson said he had not seen the lawsuit but added that his troopers' actions were appropriate from what he personally witnessed.

Baton Rouge police spokesman Sgt. L'Jean McKneely said the department does not comment on pending litigation and Sheriff's Office spokeswoman Casey Rayborn Hicks said the office had not seen the suit and could not comment on it.

The Baton Rouge police chief has defended the actions, saying there were credible threats against law enforcement.

East Baton Rouge Parish District Attorney Hillar Moore III announced recently that Mckesson, La Riva, and Marrero are three of roughly 100 arrested protesters who won't be prosecuted by his office on misdemeanor charges of obstructing a highway. In all, about 185 arrests were made in the days after Sterlings' death.

About 100 protesters arrested in BR won't be prosecuted, DA says More than half of the protesters arrested in the days following the shooting death of Alton …

Even so, McKesson, La Riva and Marrero, who were arrested July 9 near police headquarters along Airline Highway, say they were required to post substantial bail and pay administrative fees and court costs to obtain their releases, and in addition to incurring substantial attorneys' fees, they will have to pay money to have their arrests expunged.

The suit was assigned to U.S. District Judge John deGravelles, who also is presiding over a similar suit filed July 13 by the American Civil Liberties Union of Louisiana and local organizing groups on behalf of protesters.

Sterling, 37, was fatally shot July 5 outside the Triple S Food Mart.

The American Civil Liberties Union of Louisiana and other groups also filed a lawsuit last month over the treatment of protesters by police.