Random attacks cause concern in Chicago

Five youths were charged Monday in the crimes, and acting police Superintendent Garry McCarthy praised the department's response. He said there is no need for people to be afraid to walk around downtown.

"I think our reaction to it has been quick, it's been swift and it's been very effective," McCarthy said outside his confirmation hearing at City Hall.

The attacks occurred around 8:30 p.m. Saturday. Moments after a group of teens wrestled with Singer over his iPad and BlackBerry, members of the same mob attacked a 42-year-old doctor visiting from Japan. That doctor was beaten and robbed of his iPod Touch while walking in the 700 block of North Lake Shore Drive, authorities said.

"He looked like he had no idea what had happened," Singer said of the Japanese doctor, who rode with him in a squad car while helping police search for the assailants.

Both physicians were in town for the annual convention of the American Society of Clinical Oncology, which entered into a 10-year deal with McCormick Place in 2010. The five-day event typically brings in more than 30,000 doctors, vendors and other specialists from around the world.

Police sources said they have been aware of large groups of teens causing trouble along North Michigan Avenue for at least the last year. One source said the fear is the attacks could become more frequent as the weather gets warmer.