Police said Alaniz admitted to hitting Jimmie Sines.
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Sines was eventually found in the alley. He was declared dead at a local hospital.
Sines was described as a handyman who lived near the accident scene. He rode his bike everywhere, KXAS reported.
Friends told KXAS that Sines was a drifter from West Virginia who arrived in Dallas eight years ago.
Alaniz was charged with causing an accident involving death. He was sent to the Dallas County jail on $25,000 bond.