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(CNN) -- Three white Mississippi men pleaded guilty to federal hate crimes Thursday in connection with the 2011 beating death of an African-American man in Jackson, the Justice Department announced. Deryl Dedmon, John Aaron Rice and Dylan Butler each admitted to conspiracy and violating the 2009 federal hate-crimes law in last June's killing of James Craig Anderson. They face sentences of up to life in prison and $250,000 in fines, federal prosecutors said.
The 19-year-old Dedmon had already pleaded guilty to state murder and hate-crime charges Wednesday in a state court and was sentenced to life in prison. Rice, 19, and Butler, 20, made their initial appearances with Dedmon in federal court Thursday morning.
The men are among the first defendants to be prosecuted under the federal hate-crime statute that President Barack Obama signed in 2009 and the first to be prosecuted in a fatal attack, Assistant Attorney General Thomas Perez, the head of the Justice Department's civil rights division, said in a statement on Thursday's pleas.
"The Department of Justice will vigorously pursue those who commit racially motivated assaults and will use every tool at our disposal to ensure that those who commit such acts are brought to justice," Perez said. "And I note that our investigation in this matter is ongoing."
In court Thursday, all three admitted to harassing and assaulting African-Americans on several occasions in the weeks before Anderson's death, hurling beer bottles, firing slingshots and driving at them with cars, prosecutors said. They targeted people they believed to be drunk or homeless, believing them less likely to report the attacks.
They are also expected to testify against other teens implicated in Anderson's killing, two sources close to the proceedings told CNN.
They admitted to violating the Matthew Shepard and James Byrd Jr. Hate Crimes Prevention Act of 2009, named for the victims of two 1998 killings that shocked the country. Matthew Shepard, a gay Wyoming teenager, died after being kidnapped, beaten and left tied to a fence, while Byrd was a black man dragged to death in Texas by white supremacists.
Anderson's death prompted several large marches and prayer vigils in Jackson, a city of about 537,000 people. At his state plea hearing, Dedmon told the court that his crimes were the result of being "young and dumb, ignorant and full of hatred."
But Hinds County Circuit Judge Jeff Weill told him, "Whatever excuse you offer, forget that. There is no excuse."
Anderson, 47, died after he was beaten and run over by a truck driven by Dedmon, who was part of a group of seven white youths from largely white Rankin County who decided to "go f**k with some niggers" after a night of partying and drinking, law enforcement officials have said, quoting some of the suspects in the case.
Authorities have said they believe Dedmon led and instigated the attack. They said the youths climbed into Dedmon's green truck and a white SUV and drove to the western edge of Jackson, where Anderson was standing in a hotel parking lot just beyond a highway exit ramp.
On a videotape obtained exclusively by CNN, the group pulls into the parking lot and stops where Anderson is standing, although he is just off camera and not visible. The young men can then be seen going back and forth between their cars and Anderson.
Witnesses told authorities this is when Anderson's beating took place, as the white youths yelled racial epithets, including "white power." After the beating, Dedmon drove his Ford F-250 truck over him, leaving him to die, according to what some of the teens cooperating with police have told authorities.
Rice initially faced state murder charges as well, but a judge reduced the charges to simple assault because he was not believed to be driving the vehicle used to kill Anderson.
At Dedmon's sentencing Wednesday, Anderson's sister, Barbara Anderson Young, said her family was praying for "racial conciliation."
"These last months have been very difficult," Young said. "We cried. We wept. We reminisced about our beloved brother, Craig, a loss I cannot even explain. Craig was a big-hearted person who loved his fellow man."