Reporter: We're on the beat with James scoppa. Lead detective, determined to crack a big case for atlantic City's new prosecutor. I was happy when prosecutor Tyner came in and he allowed us to work on the case and investigate it like we believed it should be. Meanwhile Kim and her attorneys keep their eye on what they believe is the prize -- Jim Kauffman. Using his pictures on social media as incentive. I would get a picture of Jim Kauffman and Carole at the final four. You know, smiling. I'd put it on my brother's screen. So that when he came in in the morning, that would be the first thing he'd see, Jim Kauffman and Carole. Saying, "Yeah, so what? I killed her. What are you gonna do about it?" Reporter: But there's an unexpected canary in Kauffman's coal mine. Its coming in the form of a tip from the FBI. The feds believe Kauffman may be involved in another unrelated crime. Lo and behold, another investigation related to insurance fraud. His role as a doctor, comes up so investigators get a warrant to search his office. So they show up at Kauffman's clinic just to look at his reports. On June 13, 2017 we attempted to serve a search warrant at Dr. Kauffman's office. Reporter: Within minutes it becomes clear that this will not be a routine visit. You stay right here for me. No. No. What does he do instead of ushering them in as most of us would with the feds? No. He grabs a 9 MM. Ruger. Reporter: A police body camera's captures it all you can see and hear him. "5-11, I have one at gun point Dr James kauffma he has a weapon. Drop the gun! Drop the gun." Reporter: For 45 minutes there's a heart-unding stand off with police. Drop your gun. Reporter: At one point Dr. Kauffman threatening to take his life. I'm going to kill myself. It sure seems like Jim thinks they're there in connection with April's murder. Let's talk. I'm not going to jail for this. We have movement. Reporter: Finally, a hostage negotiator gets the disgraced doctor to surrender. Please step out to the curb. Now slowly reach down and pull your shirt up. Keep walking backwards. Watch the building to make sure no one ee is inside. This video changes everything. Reporter: The husband of a murdered south Jersey radio host and adcate is behind bars following an early morning STA off. Reporter: Investigators say that same day theyeized more weapons from Kauffman and at least $100,000 in cash. That was a game changer. After the standoff with Jim Kauffman, he goes to jail. Not for murder, but R weapons charges. He fights to try to get out and the judge would not let him out based on his conduct and that gives the new prosecutor, Tyner, a chance to really dig into the murder case. Reporter: Staing with the crime scene. So this is the house. Reporter:ut the biggest break in the case doesn't come from inside this house at all. We knew Dr. Kauffman, that there was a point in time that he was iuiring about having her killed. How did you find that out? We were able to get a witness to cooperate with us this past November. That broke the case. Reporter: Who was that witness? A former member of the pagans motorcycle club. Remember them? They're the ones Dr. Kaufman had pointed the finger at in his deposition. What motorcycle gang? The pagans. Reporter: But now, the tables have turned. One of those pagans ratting out Kauffman and not just for murder. Good afternoon everyone. Reporter: At a press conference Tyner lays out the case of an elaborate and secret double life that Jim Kauffman was leading. Treating patients by day and writing fraudulent opioid prescriptions for those pagans by night. They would come in and be patients, anall of a sudden, you had a prominent endocrinologist that W prescribing opioids and all kinds of other pain killers, wh that wasn't quite his practice. Reporter: So he's got the power of the prescription and then they've got the gang activity. Essentially they were flooding the market with opioids and selling them at a marked up price. What a bombshell. This strait-laced doctor that everyone had respected was pt of a pill mill, a drug ring. Not only that, with the pagan outlaw motorcycle gang, the and April Kauffman found out -- Reporter: Found out and according to NER threatened to expose his secret seedy double life. He started thinking about ways to engage his exit strategy you might say. Reporter: To get rid of her? To get rid of her. For the past five and a half years, ever since April Kauffman was found shot to death, there's been little movement on this case and no arrests had been made in connection with the murder. That is until today. Reporter: An explosive breakthrough in the murder of radio host April Kauffman. Reporter: Murder charges against April Kauffman's husbd Dr. James Kauffman and Reporter: But didn't the doctor have an airtight alibi? But remember that early morning stop at a convenience store? Tyner says Dr. Kauffman wasn't the shooter at he paid one of those pagans roughly $20,000 to do his dirty work and kill his wife. He went inside, and he shot April Kauffman twice. Reporter: And ironically -- that allegit man died a year and a half after April's murder of an opiate overdose. His pills? Prescribed by, you guessed it, Dr. Jim Kauffman. When I ard the details of everything, it really, really was unbelievable. I feel like this is the worst made for TV movie on the planet. Reporter: The prosecutor worries Kauffman cld be targeted by pagan members in jail. So they move him upstate to the Hudson county correctional facility as they begin gearing up for their first major trial. Finally a chance to close one of those atlantic county cold cases. And then another shocking turn. Reporter: Dr. James Kauffman dead. Officials confirm he died at 9:20 this morning. Reporter: What was your reaction when you heard this? I was snned. The story started off terrible and is ending terrible. Reporter: Dr. Jim Kauffman is dead. But how? Were you worried that he could be hurt in prison? That's always a concern. Reporter: Will justice ever be served?