(CNN) — Federal prosecutors unsealed hate-crimes charges Thursday against three white Mississippi men accused of killing an African-American man in Jackson.

One of the three, 19-year-old Deryl Dedmon, pleaded guilty to state charges Wednesday in the June beating death of James Craig Anderson. The other two defendants, John Aaron Rice and Dylan Butler, made an initial appearance with Dedmon in federal court Thursday morning and are expected to enter guilty pleas in the afternoon, two sources close to the proceedings said.

Life sentence in Mississippi hate-crime case

They are also expected to testify against other teens implicated in Anderson’s killing, the sources said.

Anderson’s killing prompted several large marches and prayer vigils in Jackson, a city of about 537,000 people. The Justice Department had been looking into Anderson’s killing as a possible federal hate crime and assisting local prosecutors in the case.

Dedmon, 19, pleaded guilty to murder and a hate-crime charge in state court in Jackson on Wednesday, receiving two concurrent life sentences. He told the court that his crimes were the result of being “young and dumb, ignorant and full of hatred.”

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. They face possible sentences of up to life in prison under the law.

Anderson 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 was initially charged with murder as well, but a judge reduced the charges to simple assault because Rice 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.”