A 30-year-old man was walking with his girlfriend in the 300-block of North Michigan Avenue, near Wacker Drive, about 12:07 a.m., when he got into an argument with a group of people, police said. The altercation with the six others became physical, and he was stabbed in the chest and back with a "cutting instrument," according to police.
A 23-year-old man, who police said was a stranger passing by, tried to intervene. He was also stabbed in the thigh, police said.
Both men were transported to Northwestern Memorial Hospital in critical condition, according to police.
No one was in custody later Saturday morning.
This is a developing story; check back with ABC7 for updates.
Sun-Times Media contributed to this report.