(CNN) — The family of Tyre Nichols filed a federal $550 million lawsuit against the city of Memphis, its police department, and what the suit said were "unqualified, untrained, and unsupervised" officers assigned to a special unit who brutally beat the 29-year-old Black man after a traffic stop in January.

Nichols was repeatedly punched and kicked by Memphis police officers following a traffic stop and brief foot chase January 7. He was hospitalized and died three days later.

The lawsuit, filed by lawyers for Nichols' mother, RowVaughn Wells, said the fatal beating was the "direct and foreseeable product of the unconstitutional policies, practices, customs, and deliberate indifference of the City of Memphis" and its police officials.

"This has nothing to do with the monetary value of this lawsuit," Wells told reporters. "But everything that has to do with accountability. Those five police officers murdered my son. They beat him to death and they need to be held accountable along with everyone else that has something to do with my son's murder."

The suit compared Nichols' beating to the 1955 killing of Emmett Till, adding that — like Till — Nichols suffered a beating "endured at hands of a modern-day lynch mob."

The reasons Nichols was stopped in his car have "never been substantiated," the lawsuit said. The officers then dragged Nichols out of his car, unleashed an unjustifiable "frenzy of force" on him and acted like "a pack of wolves attempting to hunt down their wounded prey."

Five police officers, who are also Black, were fired following an internal investigation and were indicted on criminal charges January 26.

Memphis Police spokesperson Maj. Karen Rudolph declined to comment on ongoing litigation.

CNN has sought comment from city officials, and attorneys for the five officers charged criminally.

The five charged officers were part of the department's specialized SCORPION unit, which was launched in 2021 to take on a rise in violent crime in Memphis.

Memphis police said the unit was permanently deactivated shortly after video of Nichols' arrest was released in January.

"This landmark lawsuit is not only to get the justice for Tyre Nichols in the civil courts but it is also a message that is being sent to cities all across America who have these police oppression units that have been given the license by city leaders to go in and terrorize Black and brown communities," attorney Ben Crump, who represents the Nichols family, said at a news conference.

The lawsuit said the fatal beating of Nichols went beyond five rogue officers, calling his death "the culmination of a Department-ordered and Department-tolerated rampage by the unqualified, untrained, and unsupervised SCORPION Unit carrying out an unconstitutional mandate on the streets of Memphis without any fear of retribution or consequence."

"Rather than 'restore peace' in Memphis neighborhoods, the SCORPION Unit brought terror," the lawsuit said.

"In reality, it was an officially authorized gang of inexperienced, untrained, hyper-aggressive police officers turned loose on the Memphis community without any oversight. They were instructed to strike without warning and, many times, without any valid constitutional basis."

Body camera videos and surveillance footage from Nichols' arrest were released a day later, publicly revealing the severity of the beating, drawing widespread condemnation from residents and police officials and, the county prosecutor said, contradicting what officers said happened in the initial police report.

The video prompted renewed national debate on justice in policing and reform, shaking a nation accustomed to videos of police brutality — especially against people of color. It also spurred protests and vigils in Memphis and other major US cities.

The US Department of Justice is reviewing the Memphis Police Department. The DOJ also said it would separately review specialized units across the US and create a guide for their use in addition to its review of the Memphis PD.

The five former Memphis police officers indicted in January were arraigned February 17 on criminal charges.

Tadarrius Bean, Demetrius Haley, Justin Smith, Emmitt Martin III and Desmond Mills Jr. each face charges of second-degree murder, aggravated assault, aggravated kidnapping, official misconduct and official oppression. Second-degree murder in Tennessee is considered a Class A felony punishable by 15 to 60 years in prison.

Their attorneys entered not guilty pleas on their behalf.

Police in February identified a sixth officer who was fired, Preston Hemphill, who is White. Police said he was accused of violating departmental policies including those covering personal conduct and truthfulness.

Last month, a Memphis official said that a seventh police officer has been fired and others were suspended or left the force after Nichols' death. The officer's name, and details about what the officer is accused of doing weren't immediately released.

And three Memphis fire department personnel who responded to the scene — two emergency medical technicians and a fire lieutenant — were fired, though none was criminally charged, according to the city. A city official said last month that a fourth fire department worker was suspended but no details were provided.

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