The Chicago Police Department is scrambling to explain why the parents of a 21-year-old suburban man – who suffered a serious head injury after a Gold Coast attack by a mob of teenagers – were ignored for days when they tried to file a police report.

Local Ald. Brian Hopkins (2nd) said Friday the young man, whose family wishes to remain anonymous, is in the intensive care unit at Northwestern Memorial Hospital six days after the Saturday evening incident.

Hopkins went to the hospital this week and spent several hours talking to the parents. He also talked at length to the girlfriend who described the harrowing attack in detail.

After spending the day at Oak Street Beach, the girlfriend claims she and her boyfriend were walking back to their car at around 6 p.m. in the vicinity of the 900 block of North Lake Shore Drive when they were surrounded by “20-to-25 offenders who gathered around them,” Hopkins said.

“She described a completely unprovoked attack with no warning. Her and her boyfriend were enjoying the day on the beach. They were walking back to their car minding their own business and, with no warning at all, they were surrounded by this large group and they did absolutely nothing to provoke it,” Hopkins said.

“They started a confrontation and, at some point, the victim was struck in the head and fell to the ground.”

The victim’s father had called the alderman’s office to correct him when he heard Hopkins quoted as saying there had fortunately, been no serious injuries in the latest in a series of flash mob incidents apparently orchestrated on social media.

“Witnesses who saw the attack called 911. Paramedics responded and transported the victim. The parents then called 911 to report what had happened and they had been told that police would meet them at Northwestern Hospital,” Hopkins said.

“The parents waited for several days, called a few times to see when the police were coming and grew frustrated when they didn’t get a response.”

After talking to the parents and girlfriend, Hopkins contacted newly-appointed 18th District Commander Dan O’Shea, who replaced slain commander Paul Bauer. O’Shea “responded immediately” and sent detectives out to talk to the family.

“There is a police report now. There wasn’t until recently…Police have some solid leads to work from,” he said.

“I can’t explain the delayed response….Something happened that wasn’t supposed to happen. You shouldn’t have parents in a situation like that with a loved one suffering from serious injuries wondering when they’re going to get the attention they’re entitled to from law enforcement.”

Hopkins was asked whether he believes there was an attempt to cover up the incident to avoid a black eye that could have a chilling effect on retailers, restaurants, bars and tourism.

“I would be deeply shocked and disturbed if that turned out to be the case. I expect better from our law enforcement. I don’t think that would happen. I don’t believe that’s the explanation,” Hopkins said.

O’Shea could not be reached for comment.

Police Department spokesman Anthony Guglielmi sent the Sun-Times a short emailed response that appeared to dispute at least some of the details told by the girlfriend and the victim’s family.

“I don’t have much information but the district is doing a formal review and we will report back,” Guglielmi wrote.

“What I do know is this was not a flash mob incident but a fight between two groups. Officers did respond and the district is reviewing everything.”

About an hour after the suburban man suffered the head injury, a flash mob of teenagers jumped on cars, harassed and intimidated shoppers on Michigan Avenue. One of those teenagers was arrested for throwing liquid on a police officer.

On Friday, Hopkins demanded a surge in police manpower — and better coordination between law enforcement, the CTA, retailers and private security – to nip the annual summer wilding problem in the bud and protect “the economic engine” of Chicago.

“It’s the focal point for downtown tourism, which provides a lot of revenue. If we lose that, it has a ripple effect throughout the entire city. Our tax revenue will go down, which limits our ability to pay for all of the services that everyone in Chicago relies on,” Hopkins said.