CHICAGO (CBS) — Police have run into a snag in their investigation into an early-morning accident Saturday that killed one man and injured his brother.

The Police Major Accident Investigation Unit thought they had the driver of the other car under police guard at John H. Stroger Jr. Hospital of Cook County — a 25-year-old man — but police later said they determined the man they were holding was a passenger in the other car. The driver had fled the scene and was still at large Saturday evening.

Police were not saying how much they know about the motorist whose car hit the other vehicle at Division Street and Central Park Avenue at about 5:35 a.m. Saturday.

Twenty-four-year-old Ivan Miranda, of the 2600 block of West Haddon Avenue, was pronounced dead at John H. Stroger Jr. Hospital of Cook County. Miranda’s brother was in serious condition at Mt. Sinai Hospital.

The Miranda brothers reportedly were on their way to pick up a third brother from work.

A street-side memorial at the crash site grew by the hour Saturday. Friends and family gathered to reflect on Miranda’s life.

Cynthia Chavez said Miranda was “always laughing, having fun, living life to the fullest — like that was his thing.”

“It’s sad that he has to leave this world like this,” said Joe Vargas, a close friend of Miranda’s, told CBS 2’s Chris Martinez.