The Alameda County Coroner named 49-year-old Oliver T. Williams as the man killed on BART.
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Those close to him knew him as Tyrone Hodges. Family members identified his Facebook page, under that same name.
"He always tried to help people," Aliyah McGrue said. "I'm not shocked to hear he tried to help somebody the other day."
McGrue said Hodges was her uncle.
According to BART, the victim tried to stop 39-year-old Jermaine Brim from stealing a shoe off a sleeping passenger.
During the fight, BART police believe Williams pulled out a knife in self-defense. They said he was killed with his own weapon.
"Both individuals took it upon themselves to start a fight. It's something that unfortunately happened," BART Interim Police Chief Ed Alvarez told reporters on Wednesday. "And somebody lost their life as a result of it."
Many describe the victim as a loving father.
On Facebook, his daughter posted a public message that read in part, "If you knew anything about him, you knew he loved showing off his daughter. My dad loved us, and gave us his last."
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"Tyrone was a beautiful man," Melba Douglas told ABC7 News. She knew Hodges as a neighbor and friend. Adding, his actions were entirely reflective of the man she knew.
Friends and family agreed, and said Hodges has always stood up for what was right.
"It sucks that he got killed in the process of trying to help somebody," McGrue said. "But like I said, I'm not shocked that he tried to help him. That sounds just like him."
McGrue said Hodges was just weeks away from becoming a grandfather.