Mejia, a student at the University of Illinois Chicago, was pronounced dead at the scene.
The 22-year-old Sord's blood-alcohol level was 0.236, nearly four times the legal limit for driving, according to a statement from the sheriff's office.
The accident happened around 4:20 a.m. Thursday when the Mercedes SUV Sord was driving hit a light pole, went into a ditch and rolled over, police said. Sord and Mejia were not wearing seat belts, according to the statement.
Sord told investigators he was out with friends earlier that night before picking up Mejia and heading home.
Sord will remain in police custody until his bond hearing Saturday at the Markham courthouse.