Santiago is being held in lieu of $900,000 bail. He's charged with first-degree murder.
Officials say Santiago tried to strike another car with his SUV several times on Archer Avenue on the city's South Side early Saturday morning. Each time, the second car evaded the crash, according to the Cook County State's attorney.
When the driver of the other car stopped in the 1800-block of West 33rd Street, Mendez and another passenger got out. Prosecutors say Santiago deliberately aimed at them with his SUV after accelerating, jumping the curb and crossing into a grassy area.
Mendez was struck at 6:42 a.m. Saturday, and pronounced dead half an hour later.
His death was ruled a homicide by the Cook County Medical Examiner's office.
Prosecutors say Santiago drove off on the Stevenson Expressway, and only later checked for damage. At that time he allegedly told a passenger in his SUV that he may have hit someone.
Witnesses identified Santiago, prosecutors said.
Santiago will be in court next on May 27.