Lopes was 19 years old when he was killed Dec. 21, 1969, during a melee that took place at Del Monte Manor at 1418 Yosemite St., prosecutors said. Detective Nick Borges said a packed party at Seaside's Del Monte Manor Apartment turned violent.
Chris Lopes was stabbed in his neck, stumbled to center of the apartment's parking lot and fell to his death, Borges said.
Although the Lopes family yearned to find and bring Lopes' killer to justice, the case eventually went cold.
In 2007, Seaside police investigators received information about the homicide and followed up on the leads. Detectives, however, continued to hit numerous dead-ends while investigating the case.
In 2010, the Monterey Peninsula Cold Case Project, which consists of local police detectives, an assistant district attorney and a Department of Justice forensic technician, started working on the case. An eyewitness eventually emerged after the case was reopened and gave an account of who killed Lopes.
Borges, who worked on the case for three years, helped track down Mason to the Texas suburb of Cedar Hill.
"We had a detailed interview with this person," Borges said. "They said they were close to death several years ago, and they were at a stage in life where they were prepared to get this off their chest. They wanted the truth to be out."
Mason was arrested and charged in Lopes' death. Borges said when detectives showed up to speak with Mason, the man had a look of shock on his face.
Christine Lopes, the older sister of Chris Lopes, said her brother's death was devastating for her entire family, and that it continues to be difficult to understand why he died.
"It was hard. It's still hard," Lopes said.
Chris Lopes was a freshman at Monterey Peninsula College and had been a local basketball star with a bright future when he was killed.
Christine Lopes said her brother was popular and an all-around great guy.
But Christine Lopes said she never thought the case would get solved and had lost hope until she met Borges.
"I felt like I had to do this, I couldn't quit," Borges said.
Two weeks after Lopes was killed, his girlfriend gave birth to his son, who was named Chris.
When Christine Lopes learned of Mason's arrest, she said that Mason has been able to live 42 years while her brother was never able to see his son.
She said Mason has lived and done everything he wants to and hopes he is convicted in her brother's killing.
Chris Lopes' son went on to have a son of his own -- Jordan Kausin -- who said learning of Mason's arrest has been bittersweet.
"I wish I could just meet him," Kausin said of his grandfather. "I have that love for him, just hearing so many great things about him makes me feel good."
Prosecutors said Mason has waived his extradition from Texas and will be arraigned when he arrives in Monterey County within the next two weeks.
The homicide will be the oldest cold case ever prosecuted in Monterey County, prosecutors said.