The head of the Secret Service was forced to apologize Monday after agents ordered hundreds of cancer-stricken children and their supporters to leave a park by the White House over the weekend, citing security concerns as the president was scheduled to head to a speaking engagement.

The Washington Post reported that Secret Service Director Joseph Clancy called one of the organizers of the CureFest for Childhood Cancer vigil. The organizer, Mike Gillette, said Clancy told him that he was "very sorry" and admitted that the agency "did not handle the situation well." An agency spokeswoman confirmed to the Post that Clancy had made the call and said the agency was re-examining its policy on closures.

For his part, Gillette told the paper that Clancy offered to attend one of the group's events to apologize in person and offered to have some of the children at the vigil take a tour of one of the agency's training facilities in Maryland.

The apology meant a lot, Gillette told the Associated Press, but he couldn't accept it on behalf of the children.

"There are children who were in the audience who will not be there next year at this time, and there's nothing to do or say to make this up to them," Gillette said.

The Secret Service ordered Lafayette Square cleared Saturday night as a vigil was about to begin during the two-day event. Gillette told the AP that organizers knew getting cleared from the park was a possibility, but they assumed it would be for an unanticipated threat.

"We didn't expect the president's travel across town would cause our event to be basically canceled," he said.

U.S. Park Police spokeswoman Sgt. Anna Rose said the Secret Service announced the security closure for presidential movement at 7:15 p.m. President Barack Obama spoke later that night at the Congressional Black Caucus Foundation's annual awards dinner.

The closures on Pennsylvania Avenue and Lafayette Park were "put into place based on standard protocols prior to protected movements in the vicinity of the White House Complex," Secret Service spokesman Brian Leary said in a statement emailed to The Post. "The Secret Service would like to express its regret for not communicating more effectively with this group concerning the timeline."

Gillette said Clancy sounded concerned about how officers conducted themselves. Gillette noted that officers at the park were professional and polite and seemed frustrated to be in an awkward situation. Better communication would have helped, Gillette said.

He added that if organizers knew that the closure would last hours, they could have moved the program to a nearby hotel and walked to the other side of the White House for the vigil. Instead, they were stuck outside the park with tired children and upset parents. The group was about 750 people when the park was cleared, and it dwindled to fewer than 10 by the time the park reopened around 10:15 p.m., Gillette said.

"To be ignored to the point of having your vigil canceled, it's disheartening," Gillette said. "Many children told us they went back to hotel rooms and cried."

The Associated Press contributed to this report.

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