UPDATE 1:45 p.m. Tuesday: Oakbrook Terrace Police Chief Wayne Holakovsky has confirmed with Elmhurst Patch that the call for "shots fired" at 2 Lincoln Center was a misunderstanding.
"A Commonwealth Edison customer was calling the call center in Oakbrook Terrace at 2 Lincoln Center," he said. "As she was talking to the call taker, they were conducting a fire alarm and fire drill test. Apparently the alarm went off, and the call taker said, 'I've got to go,' and hung up."
The customer called police and said "she definitely heard gun shots," Chief Holakovsky said. "We responded and asked for additional units because we wanted to make sure the building was secure.
"It's an 11-story building. We had to check the elevators, closets, stairway, all the offices, the garage. So we had to call additional manpower to search the building to make sure there was nobody in there with a gun."
UPDATE: 1 p.m. Tuesday: Fox News Chicago is reporting the call of "shots fired" at 2 Lincoln Center that resulted in evacuation of the building was actually a "misunderstanding."
During a training exercise at the building, a customer who had been on the phone with a ComEd representative called police, saying she had been told shots were fired in the building, according to Fox.
"We get a call like this we have to check it, we have to check everything," Holakovsky told Fox.
ORIGINAL STORY 12:30 p.m. Tuesday: Police officers from multiple jurisdictions are sweeping the 2 Lincoln Center building in Oakbrook Terrace floor by floor, according to dispatch reports. The incident began unfolding at about 10 a.m. Tuesday morning, after police received one call of a person with a gun in the building. This information has not yet been confirmed by Oakbrook Terrace police.
The building has been evacuated, according to a Twitter post by one employee. We're also hearing via Twitter that employees in nearby buildings are being asked to "stay put."
All stairwells and the elevator have been secured or are in the process of being secured. Officers from Elmhurst, Lombard, Addison, Oak Brook, York Center, Hinsdale and DuPage County are among those assisting Oakbrook Terrace. Police have been sending four to eight-man teams to secure each floor. One witness said a helicopter also was overhead.
The building has 11 floors and is home to ComEd and other businesses.
According to early reports, nearby Montini Catholic High School officials were told they did not need to go on lockdown.
Oakbrook Terrace Police Chief Wayne Holakovsky was not immediately available for comment. This story will be updated.