Jose Luis Magana/AP

Federal buildings in Washington and across the country will see a heightened security presence after the Department of Homeland Security announced late on that Tuesday it was beefing up protection following last week's shooting of a guard outside the Canadian parliament in Ottawa.

Secretary Jeh Johnson said in a statement that he had directed the Federal Protective Service, which stands watch over 9,500 U.S. facilities, "to enhance its presence and security at various U.S. government buildings in Washington D.C. and other major cities and locations around the country."

He didn't disclose the exact measures to be taken, saying they were "law-enforcement sensitive" and would vary by time and location. Nor did he cite any specific or credible threat against the government. The heightened posture, Johnson said, was in response not only to the killing of two Canadian soldiers in separate incidents last week but to the "continued public calls by terrorist organizations" for violence against the U.S.

The reasons for this action are self-evident: the continued public calls by terrorist organizations for attacks on the homeland and elsewhere, including against law enforcement and other government officials, and the acts of violence targeted at government personnel and installations in Canada and elsewhere recently.  Given world events, prudence dictates a heightened vigilance in the protection of U.S. government installations and our personnel.

Johnson said he was urging state and local officials to be vigilant, "particularly in guarding against potential small-scale attacks by a lone offender or a small group of individuals." So-called "lone wolf" attacks have been a top focus of law enforcement in recent years as federal authorities have cast doubt on the ability of al-Qaeda, or more recently the Islamic State, to carry out large-scale terrorist attacks on the U.S. homeland.