In the ring, boxer Stan Stanisclasse was nearly unstoppable. But outside the ring, intense jealousy from Darrell Telisme, a rival who worked out in the same gym, was building. Police say that jealousy would end in murder.

Stanisclasse took up boxing at age 16 in Palm Beach, Florida. Before long he was competing around the globe.

The guy with the heart of gold had big ambitions, and he had the talent to back them up.

Tragically, the rising star only reached the age of 23. Early on the morning of Thanksgiving in 2015, he was murdered with a single gunshot to the head at point-blank range from a Colt .45 handgun.

Darrell Telisme was a local boxer in Palm Beach, and he and Stanisclasse hung out.

Dave Lewter, Stan's longtime coach and friend, remembers how the two boxers came together. It was clear that unlike Stan, Darrell was no natural.

Undeniably, Stan had Darrell beaten across the boards. But Darrell never saw it that way. He thought he was better than Stan.

The one-sided rivalry went on for years in and out of the gym.

The night before Thanksgiving, Stan and a friend went for drinks with Darrell in downtown West Palm Beach. By daybreak, Darrell would be the suspect in Stan's murder.

"According to the witnesses, the suspect had been egging on the victim to fight him either in the ring or im any other way, and the victim was reluctant to do that," said Palm Beach Shores Police Chief Duncan Young. "The victim did not want to fight him in the ring or otherwise. Eventually, from what I understand, the suspect pushed the victim too far. And eventually they had a physical altercation down in West Palm Beach."

Stan was a much better fighter, and ended things fast, but the fuse had been lit.

In Stan's mind, things were settled once and for all.

"Stan said 'This is it, we're done, it's finished. We put that rivalry to bed,'" said Young.

When everyone went their separate ways, and Stan was locked up tight inside his Palm Beach Shores home, he thought all the drama was over, squashed. But it wasn't. A few hours later, at around 4 a.m., Darrell came back, knocking on Stan's apartment door, in the dark hours of Thanksgiving morning.

"It's my estimation and from what I've been told by witnesses that the suspect was still angry and went home and got a gun and came back and decided to finish things," said Young.

The so-called rivalry that went too far was finally over. And the man who seemed to always want to win, will still likely end up losing.

Cops say Darrell waited at his West Palm Beach home to be arrested. According to police reports, the gun and his clothes, stained with Stan's blood, were also still inside. And Darrell confessed to the crime.

"He gave himself up willingly so that nobody else was injured," said Young. "I am thankful for that."

"I will never understand how you go from somebody getting the best of you to making the decision that shooting him in the head is the best option," said coach Dave Lewter. "What makes that a good idea?"

Darrell Telisme is charged with first-degree murder with a firearm. He told police the night of the shooting was not premeditated, but rather an alcohol-fueled blur. He is being held in jail without bail.