This article has been updated as new facts have emerged.

A black power group claimed responsibility for an attack on police officers at a Black Lives Matter rally in Dallas and vowed to carry out more assassinations. Though authorities have not given specifics about the connections of "lone shooter" Micah Johnson, they have revealed that he was a New Black Panther Party and African American Defense League symphathizer.

The "Black Power Political Organization" posted the following message on Facebook hours after the shooting, which left five officers dead and six others wounded:

#BlackPower! #BlackKnights! Sniper Assassins Take Down Five Police Officers! And More Will Be Assassinated In The Coming Days! Do You Like The Work Of Our Assassins? Get Your Own Sniper Rifle And Join Our Thousands Of Sniper Assassins Worldwide In the Fight Against Oppression!

The account has since been taken down.

The Mirror reports that the same group posted the following ominous message days prior to the attack:

"Don't worry my people! Justice will be served for Alton Sterling!

"We contacted the police chief Carl Dabadie Jr. He already know what will happen to him, his wide Carla Settoon Dabadie, and his two sons, if he don't do what we want.

"So continue to support us, and (Black Knights) sniper assassin group."

Here's a screenshot of BPPO claiming responsibility and vowing to murder more police officers:

The Facebook message posted from the Black Power Political Organisation account

Authorities have not presented any details about the group nor have they confirmed whether or not it was involved in the attack.

Friday morning, the Dallas Police Department identified one of the suspects as Micah X. Johnson of Texas, a veteran who served in Afghanistan and who, according to Dallas Police Chief David Brown, told officers he was "upset about Black Lives Matter" and the "recent police shootings," and that he wanted to kill white people, specifically white officers. He claimed that "IEDs" had been placed throughout the city. He also claimed to have been working alone, though initial reports suggested it was a coordinated attack. After negotiations with Johnson broke down, police were forced to kill him using a bomb robot.

Police initially detained three other suspects, two men and one woman, but have since released them.

UPDATES: The Dallas Police Department told reporters late Friday afternoon that they found an arsenal of weapons, including rifles, ammunition, ballistic vests, and a journal containing descriptions of combat tactics, at Johnson's residence.

Dallas Mayor Mike Rawlings announced later Friday that he believed Johnson was "the lone shooter."

Authorities have also revealed that Johnson was a Black Power sympathizer, who had expressed interest in the New Black Panther Party and the African American Defense League.