LENOIR CITY, Tenn. (WVLT) -- The past five months have been unbearably difficult for Vicky Johnson. She said her son Tony died of a drug overdose last November at the age of 29. She said his 11-year-old daughter found his body inside their Lenoir City home.

"I screamed, I begged and tried CPR, but he had been gone too long. I asked God to just give me my son back," said Johnson. "He was me and my granddaughter's world."

Johnson said her son had struggled with drug addiction, but he was on his way into full recovery. Tony had taken on a new job, but that job may have been too strenuous for him and his arthritis, according to his mother. Johnson said her son was always sore and had a setback moment where he used again.

"One mistake and he's gone," cried Johnson.

The Lenoir City Police Department said Tony Johnson died from a heroin overdose that was laced with Fentanyl, a deadly drug that can be 100 times more potent than morphine.

His mother said that Tony did not know Fentanyl was in the heroin, and now she wants the person that sold it to him to be held responsible.

"He didn't do this on purpose, he didn't know what he had that other person did, and they knew they were taking a chance on killing somebody, but they wanted the money more," said Johnson.

Lenoir City Police Chief Don White said his department is actively investigating Tony's death, and he expects someone could be charged.

"My investigators are currently working with the 9th Judicial Drug Task Force, and they are still tracking leads. It is still an open investigation and it's going positive, and we hope to have indictments on that case sometime this year," said White.

White explained that the process is long and difficult in overdose cases, primarily because of the lack of cooperation among witnesses.

"It's just difficult, we get very little cooperation from witnesses that are involved, and we've got to really dig deep at the crime scene to have a successful prosecution. If that individual and that heroin was laced with Fentanyl and they knew it, you gotta prove that," explained White.

So far, 11 people face homicide charges after overdoses in Knox County. The Loudon County Sheriff's Office has charged one man with Reckless Homicide after he was accused of providing the financial means for another to buy drugs. The Lenoir City Police Department said they have charged two individuals with murder or homicide after an overdose, and they expect Tony Johnson's case to be the third.

His mother told Local 8 News that her son was a good man who fought hard to break his addiction.

"I know people will say, 'Okay, he's the one that put the needle in his arm.' I am not denying that, and I am not saying he is perfect," said Johnson. "To a lot of people, these folks are just drug addicts, but to me he was my everything."