On the day of his murder, Shakur was involved in a brawl with Crip member Orlando Anderson on the floor of the MGM Grand casino. Earlier, at a local mall, Anderson had tried to steal a Death Row Records medallion from one of Shakur’s entourage—a Mob Piru member—sparking a fistfight. Spotting Anderson at the casino, the hot-tempered rapper attacked. The LAPD insider says a former leader of the Crips admitted that Shakur’s death was revenge for this beating. “It was simple retaliation: you mess with one of ours, we will mess with one of yours,” the source says. “If Orlando had never been jumped in the hote,l they never would have killed Tupac that night.” As Shakur lay dying on the Las Vegas street, a police officer frantically asked him who pulled the trigger. Tupac’s response? “F— you.” They proved to be his last words. Las Vegas Police Department detective Dan Long feels sure that both Shakur as well as Knight, who was behind the wheel of the fatal car, were familiar with their assailant. “My belief is they both knew,” he tells PEOPLE. “The cars were two or three feet apart when the shooting occurred. Tupac was the passenger, [and] he would have been right up against him in an extremely well-lit part of town.” Considering Shakur had survived a similar ambush in the lobby of New York’s Quad recording studios in November 1994, it’s possible he felt he would live and seek vengeance outside the purview of law enforcement. (He clung to life for six days before succumbing to his injuries.) Long attempted to set up an interview with Knight over the course of his investigation, but he refused to speak. Why? “Don’t want to be a snitch,” says Long. “He never actually said that, but that would be my perception.” His silence on the matter, not to mention his shadowy reputation—he’s currently serving a prison term on unrelated changes—sparked rumors that he was somehow involved in Shakur’s murder. “Some people thought Suge had Tupac killed because he was trying to leave Death Row and start his own label,” says the LAPD source. “That’s always common in the music industry: the artist wants to leave because they aren’t being paid what they think they should be paid and feel like they are getting ripped off. But immediately after Tupac was shot [in Las Vegas], the next day there were murders all the way back in LA because the Compton Mob Pirus (which Suge was a part of) knew that the Southside Compton Crips were involved.” Long also believes that Knight was not involved, simply because he was also a victim. Though Shakur’s body absorbed the bulk of the bullets from the semi-automatic pistol, Knight was struck in the head by fragmentation. “Who would actually set something up and put themselves in the firing range?” Long observes. One recent documentary makes the bold claim that Shakur was the unintended victim of a plot to assassinate Knight, hatched by the mogul’s wife, Sharitha. She strongly denied the accusation to PEOPLE, saying, “If I wanted to kill Suge, believe me, his ass would be dead. I don’t have to make an attempt on his life with an innocent person, whom I was very fond of, sitting in the car.” The most prevalent legend is that Shakur’s death was the result of the East Coast/West Coast hip-hop feud with Biggie Smalls. Death Row was battling Smalls’ label, Bad Boy Records, and the pair had already traded shots on a number of diss tracks, notably Shakur’s vicious “Hit ‘Em Up,” in which he rapped, “That’s why I f—ed your bitch, you fat mother—-er…Now you’re about to feel the wrath of a menace.” Smalls’ murder six months later in similarly unsolved drive-by shooting would forever link them in death, but the LAPD source doubts it was a rap rivalry pushed to the brink. “The media blew up the East Coast/West Coast thing. Mob Piru were responsible for Biggie’s death and Compton Crips were responsible for Tupac. Biggie and Tupac ended up being pawns in this whole thing.” Long also denies ever finding a link between the two murders. Law enforcement conducted an interview with Anderson and even served a search warrant at his home, but it never yielded enough evidence for an arrest. He was killed in an unrelated shootout a year after the murder. With a major suspect dead—as are a disturbingly high number of people of interest in the case—the investigation is at an impasse. “There are a lot of land mines in this case. It’s been on my plate for 16 years and it’s one of those cases I wish I could finish,” says Long. “I don’t believe there was any justice for Tupac because we never finished the investigation, [or] even came out and said directly who the suspect is. Without an arrest we can’t do that and there can’t be an arrest because he is dead.” As the LAPD source says sums up, “It’s not what you know, it’s what you can prove.” Reporting by CHRISTINE PELISEK. This story originally appeared on PEOPLE.