(CNN) – In the late 90s, two of hip hop’s biggest stars—Tupac Shakur and Christopher Wallace (aka Biggie Smalls, Notorious B.I.G.) were gunned down six months apart in eerily similar fashions. According to witnesses, both were passengers in vehicles, stopped at busy intersections, but police never received solid leads to arrest a suspect for either of the seemingly targeted shootings.

On September 7, 1996, Marion “Suge” Knight, then head of Death Row Records, was driving Tupac Shakur, his multi-platinum recording artist, to a party in Las Vegas after attending the Mike Tyson-Bruce Sheldon boxing match. Their security team was in separate vehicles. While stopped at a busy intersection just off the Las Vegas Strip, witnesses say a white Cadillac pulled alongside, and a gunman in the backseat fired multiple rounds from a semiautomatic gun into Knight’s vehicle.

With Shakur bleeding in the passenger seat, Knight made a u-turn, driving over a street median, and ultimately coming to a stop blocks away.

Las Vegas bicycle police nearby, who heard the shooting, followed Knight’s vehicle. The white Cadillac sped away.

Cathy Scott, who was one of the first reporters on the scene and author of “The Killing of Tupac Shakur,” tells CNN the failure to secure the actual scene of the shooting and interview witnesses immediately doomed the investigation. Las Vegas police said witnesses were not forthcoming with detailed information.

There are several possible motives for the murder.

One theory is that the shooting was payback for a fight caught on casino surveillance video three hours before the shooting. The man who was beaten that night, Orlando Anderson, told CNN a year later that he had nothing to do with the crime. Eight months after that interview, Anderson was killed in what police described as a gang shoot-out in Los Angeles.

Another theory focuses on the “gangsta” lifestyle of the hip hop world at the time and a publicized East Coast-West Coast rap war between Knight’s Death Row Records in Los Angeles and Bad Boy Entertainment in New York, which represented rapper Biggie Smalls. Shakur and Smalls had been embroiled in verbal sparring through their music.

Six months after Shakur’s shooting, Smalls came to California to promote an upcoming album entitled “Life After Death” and told a San Francisco radio station that he wanted to “squash” rumors of the East Coast-West Coast battle.

Four days later, on March 9, 1997, when leaving a music industry party at the Petersen Automotive Museum in Los Angeles, Smalls was shot and killed. Los Angeles police said a lone gunmen pulled alongside the suburban and opened fire on Smalls, who was in the passenger seat.

The main theory behind Smalls’ shooting: payback for the slaying of Shakur six months earlier.
 
Retired Los Angeles Police Detective Russell Poole, who worked on the Smalls’ case, tells CNN that he believes Suge Knight was behind the murder, even though the Death Row Records’ boss was serving time on a probation violation at the time.

“Suge Knight ordered the hit,” Poole says, adding that he believes it was arranged by Reggie Wright Jr., who headed security for Death Row Records.

Poole goes even further, stating that he believes Knight was behind the shooting of Tupac Shakur as well. Poole says Shakur’s bodyguards told him that the rapper planned to sever ties with Knight’s Death Row Records which could have cost the company millions of dollars.

“That theory doesn’t even add up,” says Scott, who wrote “The Killing of Tupac Shakur,” noting that Knight was sitting in the driver’s seat next to the rapper. “Open fire on my car, but try not to hit me?”

Reggie Wright Jr. told CNN he had nothing to do with either murder, and Suge Knight has repeatedly said he had nothing to do with the crime.

But two months after Shakur’s killing, Knight talked to ABC News and one quote seems to follow the former record company executive:

“If you knew who killed Tupac, would you tell police?” To which Knight responded: “Absolutely not. It’s not my job. I don’t get paid to solve homicides. I don’t get paid to tell on people.”

Both the Los Angeles and Las Vegas police departments say the investigations are still open.