President Obama took a walk Wednesday – but not just any stroll on the South Lawn of the White House. He went outside the secure confines of the complex to chat with normal people on the streets of downtown Washington.

And with Obama’s unusual departure from the bubble, the men and women of the Secret Service who are responsible for protecting his life faced a period of heightened alert.

Encouraged by the warm weather, President Obama shuns his convoy and takes a walk to the U.S. Department of the Interior, surrounded by secret service agents. (Reuters)

The Secret Service prefers to have the president in controlled situations, and plans far in advance of scheduled appearances to carefully examine his travel routes and event sites.

Wednesday morning’s stroll, which was captured on a White House video, was far less structured.

Some of the normal civilians whom Obama approached on his walk gasped to see him out and about, close enough to touch (and close enough for one elated woman to hug).

Secret Service agents rarely smile while shadowing the president. But the ones on Obama’s protective detail for the Wednesday stroll, visible on the White House video, looked particularly on guard as a group of three young men excitedly ran over to greet the president and shake his hand.

Witnesses said that, in addition to the agents in the immediate vicinity, the Secret Service established an outer ring of protection.

Secret Service spokesman Ed Donovan wouldn’t specify what additional steps the agency takes to protect the president during such periods. He said the agency tries to balance security and access and doesn’t want to turn the president and first family into prisoners of the White House.

Since Wednesday’s stroll was “off the record,” or unscheduled, the risks of a disruption were lower, Donovan said.

“Any time the president leaves the White House complex there are risks involved,” Donovan said, adding that the Secret Service uses its knowledge to mitigate those risks. “Off the record movements can be used to our advantage since there is an element of surprise. If something a protected [person] does is not on the schedule then presumably someone wishing to disrupt an event or do them harm is unaware of it as well.”