CHICAGO (CBS)– An all-out manhunt is underway, after a 28-year-old woman was shot in the Fulton River District by a man on a bicycle earlier in the day.

The man wearing black is seen on surveillance video on the bike after shooting the woman in broad daylight. Police released new images of the suspect on Thursday.

Police have released several surveillance photos of the suspected shooter.

Police also released video secured by detectives.

According to the Chicago Fire Department, the incident took place at 212 N. Milwaukee Ave. just before noon. The scene is on a disjointed terminal block of Milwaukee Avenue that runs only between the intersections of Lake and Canal and Fulton and Clinton streets – flanked by the Union Pacific-West Metra tracks at one end and the Chicago Transit Authority Green Line at the other.

At lunchtime, the streets in the area are filled with people from nearby office buildings in the fashionable district – walking to and from restaurants. Police said they believe that is just what the victim might have been doing when the man pulled up to her on the bicycle – and they believe she might have been targeted.

On Wednesday night, police were highly visible as the aggressively searched for the gunman on the streets of the busy Fulton River District.

Police Supt. Eddie Johnson said the woman was walking with two acquaintances when a lone gunman on a dark-colored mountain bike pulled up, extended his arm, and fired a single shot. The gunman passed by a group of other people and went directly to the woman, Johnson said.

Witnesses said the gunman did not say anything before firing the shot.

“We were taking a measurement. We heard a pop sound – thought it was a backfire, came to the rail, and saw the lady on the ground,” said Union Pacific employee Charles Williams.

Another witness told CBS 2 he saw the woman “sprawled” on the ground after the shooting and she did not appear to be moving. He also said four to five people tried to help her before police arrived.

The witness said he flagged over a police officer who was in the area for an unrelated incident.

“In the middle of the afternoon downtown,” Williams said in disbelief.

Detectives returned hours after the shooting, searching for more surveillance video from the Union Pacific railroad yard.

“We were just having a cigar I was talking to the gentleman inside, and all the sudden we heard this massive bang,” another man said.

Police were back at the Milwaukee Avenue cigar shop near the scene Wednesday night, looking for evidence that could lead them to the shooter on the bike.

“We didn’t hear any screams or anything like that, and the bicycle rode by, and we didn’t really know what was going on,” said the man who had been smoking the cigar.

Johnson said the gunman had a dark complexion and was wearing a black baseball cap, a dark T-shirt and dark pants, and light-colored gym shoes. He was also wearing a backpack.

The gunman fled northwest on Milwaukee Avenue on his bicycle, Johnson said.

“The incident did not happen in an area known for gang conflict, Johnson said. “It appears right now that the victim might have been targeted by the offender.”

The woman suffered a gunshot wound to the back and was taken to Northwestern Memorial Hospital. She underwent surgery Wednesday afternoon and her condition was stabilized, Johnson said.

The woman is expected to survive.