The situation on South Broad Street was potentially volatile.

Protesters wanted to deliver thousands of petitions to Comcast Corp. executives and directors after a public meeting at the Kimmel Center in May. They were upset over Comcast's proposed acquisition of Time Warner Cable Inc.

The executives and directors didn't want a confrontation.

Standing between the sides was Joseph Clancy, 59, a bald man with ramrod posture in a blue suit, yellow tie, and white shirt, who had guarded President Obama and his family as a member of the Secret Service.

Clancy calmly accepted petitions on behalf of Comcast, defusing any incident.

It was vintage Clancy. The Havertown native was unflappable, respectful, and a complete professional, say those who were there.

But Comcast will now have to do without Clancy, who on many days greeted employees with a friendly hello in the Comcast Center lobby.

On Wednesday, Obama brought Clancy back to the Secret Service as interim director of the beleaguered agency after Julia Pierson, as expected, resigned as its head.

Pierson had been grilled by lawmakers in testimony on Capitol Hill on Tuesday over the knife-carrying fence-jumper Omar Gonzalez, who had entered an unlocked White House front door on Sept. 19.

Top Democrats were calling for an investigation, and Obama agreed that changes were necessary for his protection.

In turning to Clancy, Obama is leaning on someone he knows. Clancy's last position was as special agent in charge of the presidential protective division. He retired in 2011.

"I appreciate [Clancy's] willingness to leave his position in the private sector on very short notice and return to public service for a period," Obama said, noting that an independent panel of experts would look at the fence-jumping incident.

At Comcast, Clancy did not provide personal security for Brian Roberts and other top executives, as he did with the president. Instead, he had responsibility for the protection of Comcast's hundreds of call centers, warehouses, and technology facilities, where tens of thousands of employees work.

Clancy also was involved in the investigations into thefts of cable-TV service or equipment, such as set-top boxes. The company promoted him to executive director of cable security in May.

Comcast officials said Clancy's Secret Service appointment came "out of the blue" Wednesday afternoon. In a statement, Comcast said: "We are highly confident he will be an outstanding interim leader for the Secret Service and we wish him the very best."

D'Arcy Rudnay, Comcast's chief communications officer, said, "We're sad to see him go and we'd love to get him back."

Clancy resigned from his Comcast position.

"You could not have found a better person to take on this responsibility," said Rep. Chaka Fattah (D., Pa.). "This is someone the country can be confident in."

Fattah predicted that under Clancy, "I think the leadership that is required can be provided."

He added: "Everybody who knows anything about him says one word: professional."

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Inquirer staff writer Jonathan Tamari contributed to this article.