A Suffolk drug dealer pleaded guilty Thursday to manslaughter in connection to a fatal overdose . 

The plea made James Fava the first person in New York state to be convicted of a charge stemming from a fatal overdose. 

Bryan Gallagher was 27 years old when he was found dead in his Oakdale home. His family says they knew he had been struggling with heroin addiction but hoped he would find a way to recover.

"We just wanted to get that manslaughter charge, and hopefully let the drug dealers know…there are going to be repercussions and the DA's office is going to go after them," said Gallagher's father Michael. 

Getting a conviction on manslaughter charges in a drug case is challenging, according to legal experts. Prosecutors need to prove the defendant recklessly caused the victim's death. In this case, prosecutors say they had multiple text messages from Fava to Gallagher warning him about the potency of the drugs.

Tanya Rickoff, the assistant district attorney, said Fava warned Gallagher that the substance was "too strong for him" and to be careful with it. 

Lab tests confirmed that what Gallagher ingested wasn't heroin laced with fentanyl. It was only fentanyl. 

As part of the plea deal, Fava will get four to six years behind bars when he is sentenced in January.

Gallagher's father says his family started a foundation in his son's name.

"It just gives us peace of mind. It gives us something to work for…Something for a family to live for. To help other people," said Gallagher. 

Fava's family and attorney did not speak to the media after court. 

Prosecutors say they are hoping this case will prompt the state Legislature to create a criminal statute specifically for fatal drug cases. They say at least 20 other states already have those on the books.