The two strangers argued before boarding a GET bus in 2011, then sat apart as the bus traveled along Pioneer Drive.
As they entered the 3100 block of Pioneer, one of the men walked to the front and told the driver he was getting off.
That man, Richard Joseph Gomez II, then approached the man he had argued with and stabbed him twice in the chest, killing him. He fled but was arrested the same day.
Gomez later told authorities he heard voices urging him to stab 24-year-old Lorenzo Hernandez.
In sentencing Gomez on Thursday to 26 years to life in prison, Judge Gary T. Friedman said the "cruel, cowardly, callous" stabbing was a senseless crime.
The judge said Hernandez was seated and posed no threat when Gomez gripped a knife with an 8 1/2-inch blade and plunged it into the other man's chest the morning of Aug. 9, 2011. Both stab wounds penetrated Hernandez's heart.
A jury convicted him of first-degree murder in January of last year. He was later found sane at the time of the killing.
Lillian Marie Castellon, the mother of Hernandez, told the court her son was a loving person with lots of friends. He enjoyed camping, cooking, dancing and traveling, and had been looking forward to celebrating his 25th birthday.
Castellon, 55, said Hernandez never hesitated to express his love.
"When he was a toddler, he'd say, 'Mama, stay in my heart forever,' and put his hands to my heart," she said. "I said, 'always and forever.'"
Even as an adult, Hernandez sent her cards and wrote "stay in my heart forever," Castellon said.
"Richard, when you stabbed my son you stabbed me as well," she told the defendant.
Gomez, 39, never looked at her. He faced the judge throughout the proceedings.
The nature of the argument between Gomez and Hernandez was never determined, prosecutor Art Norris said afterward. He said Gomez provided three different stories regarding what the two said to each other.
Friedman, reading from a probation report regarding Gomez's prior arrests and long history of drug abuse, noted the defendant said he drank alcohol and smoked pot daily at the time of the killing. He first used heroin when he was 21, and last used it around the time he stabbed Hernandez.
Gomez said in the report he used PCP twice a week from 1989 to 1991, the judge said. He also used methamphetamine.
Friedman said Gomez told probation officials he wished he could take back the killing of Hernandez.
Gomez's lawyer, J. Anthony Bryan, objected to the presence of the media at the sentencing hearing. He said paperwork to film or take photographs was not timely filed.
"I know the media is accorded all sorts of exceptions to the law, all of which I disagree with, but that seems to be the trend," he said.
Friedman allowed the media to film and photograph the proceedings.