"Jimmy The Clam" was a capo in the Gambino fam and got whacked together with his son cuz he had some beef with Gaggi and Roy Demeo,blamed Gaggi that he was an informer and was takin some territory and Roy DeMeo cheated his son "Jim Jim" on some cocaine deal and he was exposed on some children's charity scam and Castellano decided to whack Eppolito.He also was the uncle of Louis Eppolito the NYPD officer and his partner Stephen Caracappa murdered for the Lucchese crime family.Heres some articles bout the situation...

"As Eppolito exhaustively revealed in his auto-biography ‘Mafia Cop,’ he had become a darling of the Media during the 1970s and 1980s. The tabloid newspapers of New York of that era reveled in detailing the hard-nosed cop’s exploits, portraying Eppolito as a variation of John Wayne and ‘Dirty Harry,’ walking the streets of the Big Apple wearing the uniform and badge of the NYPD. Eppolito was seen as on a mission to protect ordinary citizens from the thieves and drug dealers that with each passing year were becoming more violent.
Eppolito, however, was serving more than one Master. According to Mafia protocol, and his own auto-biography, Eppolito was loyal and showed "Respect" to his father and Uncle Jimmy the Clam and his son ‘Jim- Jim,’ all three of which were ‘Made’ members of the Gambino Family, meaning they had each murdered at least one person on orders of their Godfather. By extension, Eppolito showed the same regard and "Respect" for the Gambino Family Godfather, Paul Castellano. At that time Paul Castellano was at the height of his power and influence; he lived in a mansion called the "White House" on Staten Island’s appropriately named ‘Todt Hill,’ so named by early Dutch settlers, which means "Death Hill." Castellano controlled one of the largest Mafia families in America; the Gambinos were into just about everything Evil and illegal; hijacking trucks and fencing the stolen goods; drug trafficking; credit card rip-offs; a stolen car ring; the production and distribution of pornography, including child pornography; murder for hire."---written by J. R. de Szigethy

Eppolito and his son were involvement in a children's charity scam that had been supported by, among others, First Lady Rosalynn Carter and Senator Edward Kennedy. the charity was set up by James Eppolito and the money was supposed to go to a worthy cause but the money was pocketed by Epollito.
When the scam was exposed on a "60 Minutes" television episode, one of the photographs showed Jimmy Jr. and the wife of the president posing together. Castellano was concerned that Eppolito had brought heat on the gambino's and President Carter's embarrassment might cause him to seek retaliation on the Gambino Crime Family.
In late 1979, Eppolito told Paul Castellano that Capo Anthony Gaggi and Soldier Roy DeMeo were drug trafficking. Eppolito claimed that DeMeo had cheated Eppolito's son, a Gambino soldier, in a cocaine drug deal, Eppolito Jr. was $7,000 out of pocket after the deal. In addition, Eppolito accused Gaggi of being a police informant and infringing on eppolitto's territory. Eppolito asked Castellano for permission to murder Gaggi and DeMeo. However, Castellano broke his own rules and sided with Gaggi and DeMeo. He then gave them permission to murder both Eppolito and his son. Eppolito thought he was still a powerful capo and that Castellano would side with him in the dispute however he didn't realise how close Gaggi was to Castellano and this stacked the odds in gaggi's favour.
On October 1, 1979, James Eppolito and his son were driving their 1978 Ford Thunderbird when they pulled over and gave Anthony Gaggi and Roy DeMeo a lift they decided to drive to the Gemini Lounge to solve their dispute. Gaggi sat in front with James, Jr., DeMeo and the senior Eppolito sat in the back. During the journey, the elder Eppolito knew that he was going to be whacked and decided he had to get out of the car. He told his son to stop the car so he could get out and go to the toilet. the car pulled over in Coney Island, Brooklyn before the eppolitos could do anything Gaggi and DeMeo shot and killed both Eppolitos. However, a witness alerted an off-duty policeman, who soon found Gaggi walking away from the crime scene. After a brief shootout, the policeman wounded Gaggi in the neck and arrested him. Although charged with the Eppolitos' murders and the attempted murder of the police officer, Gaggi was only convicted of assault. Gaggi was sentenced to 5 to 15 years in federal prison. Because DeMeo went in a different direction to Gaggi as they left the scene, he was not arrested or identified by the witness.

the crime scene was investigated by corrupt NYPD Detective Louis Eppolito and he describes what he saw in his autobiography:

"It was difficult, but I went over to the sheets they had spread over two bodies. I read the two toe tags. The first read 'James Eppolito, Jr.' When I pulled back the sheet, Jim-Jim's head was a mess. It was nothing I hadn't seen before in twelve years on The Job. But all that blood, and Jim-Jim's brain blasted away, it really upset me."

"Then I went to the old man. I don't know how I managed to pull his sheet away, but I did. Uncle Jimmy's face was just absolutely destroyed. His jaw and bottom lip were totally gone, torn off, giving him this long, buck-toothed look."

"And he had tattoos - the gunpowder marks that are left when you're shot at close range - all over what was left of his head. I cleaned him as best I could, combing his hair and washing the blood off his face. But water kept pouring out of his eyes, like he was crying."

source..
www.americanmafia.com & http://mafia.wikia.com