When the world's most important leaders converge on Chicago for the G8 and NATO summits, the most elite marksmen will, too.

State and local SWAT teams have been surveying buildings around Michigan Avenue, the Loop, McCormick Place and O'Hare International Airport looking for the best views of streets, sidewalks and nearby buildings.

“They'll be able to shoot the head off a nickel from 500 feet,” according to a source close to planning the events.

“It's natural for us to take a survey and to pinpoint where a threat may come from,” adds a U.S. Secret Service spokesman who says the agency has started walk-throughs of building locations that will be used for the conferences. The agency is overseeing law-enforcement details for the events.

Sharpshooters are necessary for the many motorcades packed with heads of state going from meeting to meeting—and party to party, a source says.