BOSTON (WHDH) -- Former mob boss James "Whitey" Bulger will testify at his trial next year on charges that he participated in 19 murders, his attorney said Monday.

Bulger’s lawyer, J.W. Carney, said Bulger will give the name of the Justice Department official -- not an FBI agent -- Bulger says gave him immunity for his alleged crimes.

“Our client, James Bulger, has made it clear to us; he is going to testify at this trial,” Carney said.

That was the bombshell Whitey Bulger's lawyer dropped in Monday’s hearing. Up until now, the public has only seen Bulger -- but come Bulger’s trial in March, his lawyer promises Whitey will speak under oath.

“You will hear James Bulger testify about everything,” Carney said.

Whitey wants to tell his story to the jury, and relatives of Bulger’s alleged victims say they'd love to hear Bulger talk.

“Satisfying just a bit…I’ll be satisfied when he’s convicted,” said Steve Davis, brother of alleged Bulger victim.

“I’d like to know why he’d kill somebody that he had nothing to do with. Why would he take somebody’s life in the first place, let alone somebody that he didn’t even know? That would be one of my questions,” said Patricia Donahue, widow of alleged Bulger victim.

Bulger's lawyer says the accused killer will tell all.

“We are going to ask our client on the stand about everything,” Carney said. “We have no secrets.”