Police said a 47-year-old man was walking on the sidewalk in the 300-block of North Dearborn Street when he was approached by two people.
The two people asked the victim for money and then punched him in the face, knocking him to the ground, hitting his head, police said.
Officers found the victim unresponsive with a critical head injury when he was transported to Northwestern Memorial Hospital, where he died a short time later.
Authorities have not released the identity of the victim.
Witnesses stepped into try to save his life.
Patrick Mix, who is visiting from Buffalo, N.Y., said he was pulling up to the valet just as the attack happened.
"Right outside the House of Blues I seen a man down and he was getting chest compressions," he said.
There are several surveillance cameras around this area and police are reviewing video as they continue their investigation. No one is in custody.
Neighbors living nearby woke up to the news of what happened steps outside their doors.
"On the one hand, you don't want to be too afraid to live your life, but at the same time at this point, the potential exists to be seriously hurt for seemingly no reason unprovoked, surprise, that adds a layer of concern that affects your behavior," resident Ethan Brewer said.
Donna Leonard has lived here for over 47 years. She heard all of the police activity last night.
"Right now, my stomach is in knots, and I'm just walking around the neighborhood .... and I'm constantly with my head on a swivel I've never seen it this bad," resident Donna Leonard said.
This after she walked past another violent attack on Michigan Avenue on Monday.
"A few minutes before it happened, who would expect something like this," Leonard said.
In that case, police tell us a woman visiting Chicago from out of town was walking out of the Burberry store when the suspect grabbed a decorative log used for holiday displays, and hit her with it.
Both of those attacks happened in Alderman Brendan Reilly's 42nd Ward. ABC7 did reach out to him for a comment, but have yet to hear back. Chicago Police are looking at surveillance video but said no one has been arrested