Paliatsos, who was in critical condition, was being treated at Mt. Sinai Hospital.
A third person in the back seat was unhurt and was helping state police with the investigation.
The shooting took place on the southbound Stevenson at Central Avenue just before 4 a.m.
No one is in custody.
Police believe the shooting stemmed from an argument at a nightclub.
Lopez's daughter and ex-wife were mourning his loss Tuesday. Ten-year-old Alexis Lopez held a framed picture from last month's Daddy-Daughter Dance that was to be her Father's Day gift for her dad. Now the photo will serve as one of her last memories of him.
"He was a phenomenal person, a phenomenal father," said Nancy Zambrano, Lopez's ex-wife. "No matter what I do, it is never going to bring him back. But I do want them to know that the only way for him to be in peace is for them to catch them."Zambrano said Lopez was a devoted father who saw Alexis often. They went to a movie Saturday.
"Whoever it is, could they please turn them in because this really hurts my feelings," said Alexis.
Lopez's family says he was with his friends at Spy Bar, a River North nightclub early Tuesday morning when what had been a fun night among friends took a bad turn.
"They were trying to do the right thing and help out that other girl. Unfortunately, wrong place at the wrong time," said Matthew Lopez, victim's nephew. "Some guy was beating up his girlfriend and one of my uncle's friends had noticed that and had went to go and help out that girl and I guess that is when the fight started."
Police responded to a fight at about 3 a.m. and dispersed the crowd. Illinois State Police said the incident escalated into a shooting nearly an hour later in the outbound lanes of the Stevenson Expressway near Central Avenue.
"It appears that the altercation continued onto the expressway at which time the offender went alongside the vehicle on the lefthand side and began to shoot at the vehicle," said Lt. Luis Gutierrez, Illinois State Police.
A bullet fatally struck Lopez who was in the front seat of the Ford Excursion. Paliatsos, who was also hit three times, was able to pull over on the side of the Stevenson while the offenders got away. Their car is described as a silver, newer model Chevy Trailblazer, possibly an SS with tinted windows.
In the meantime, Lopez's relatives remember him as a family man who was going back to school to be a chef. They hope the offenders are brought to justice.
"It definitely makes you realize a lot about this gun violence with the gun laws . I never really thought it was a big issue before, but now that it hits my family, I definitely notice it," said Lopez.
State police are checking surveillance video from near the River North nightclub and also the Ontario feeder ramp to see if that will help them in the investigation. They ask anyone with information to contact authorities.
