The mother of a teenager shot and killed by a Union City police officer told Channel 2 Action News the acting U.S. attorney has launched a criminal investigation into her son's death.
 
After the second grand jury chose not to indict the officer who shot Ariston Waiters, his mother, Freda Waiters, vowed to keep fighting. Friday she brought that fight to the U.S. Attorney's Office.
 
"I won't rest, justice must be served," Freda Waiters told Channel 2's Matt Belanger.

[READ: Teen shot, killed by Union City police]

Freda Waiters reaffirmed her determination to fight after meeting with acting U.S. Attorney John Horn Friday afternoon.
 
She said Horn told her the federal government is opening a criminal investigation into her son's death.
 
"My son did nothing wrong, and he was shot like an animal," Freda Waiters said.
 
"They were very familiar about this case already and they will continue with the efforts and information our office has just given them," private investigator T.J. Ward said.

It's been 3 1/2 years since Union City police Officer Luther Lewis shot Ariston Waiters twice while he was unarmed, facedown in handcuffs.

[WATCH: Mother vows to continue fight after no indictment of officer]

"Ariston Waiters died senselessly, died violently and died at the hands of a rogue officer," family spokesman Marcus Coleman said.
 
Fulton County District Attorney Paul Howard reopened the case after a Channel 2 Action News/Atlanta Journal-Constitution investigation uncovered new evidence in May.
 
Aug. 6 a second grand jury chose not to indict Lewis. Freda Waiters said she is determined to prove her son has not died in vain.
 
"I just want the right thing done for my son. I want truth and the facts," Freda Waiters said.

Ward told Belanger that Horn will review the evidence and conclusions of his investigation and will determine if any charges should be filed.