The top U.S. diplomat came to Ottawa for the day to show American solidarity with their Canadian friends and top ally.
He delivered that message Tuesday with a mix of elan and gravitas, at a joint press conference in the foyer of Foreign Affairs headquarters, opening his remarks in flawless French by thanking his "cher ami," Foreign Affairs Minister John Baird.
Kerry said Canada and the U.S. would "work quietly and carefully in the next days and months" to strengthen an already close security relationship.
"Canada and the United States are now in discussions — not with any sense that things weren't done, or that there is some information that we didn't somehow share or have — but rather with a view to making certain that every possible stone is turned over, every possible policy is reviewed because our obligation, obviously, is to protect our citizens," Kerry explained.
Kerry's upbeat remarks appeared aimed partly at assuaging any possible American jitters in the aftermath of last week's attacks that left two Canadian Forces soldiers dead in Ottawa, after an attack on the War Memorial and Parliament, and in Quebec.
Canadian officials have already mounted a diplomatic blitz in the U.S. to emphasize Canada's commitment to border security.
Kerry said both countries would continue to intensify law enforcement co-operation, border protection and intelligence sharing.
"I'm confident we'll come up with some tweaks, some changes, some additions that will promote even greater security than we have today."
Senior State Department officials, who briefed reporters on Kerry's plane ride to Ottawa, also played down any suggestion that the U.S. had concerns about Canada in the wake of the attacks.
"With every one of our bilateral relationships, we are consistently and constantly looking for ways to deepen that level of co-operation, and I'm sure that's the case with Canada as well," said one official, who spoke on condition they not be named.
"But in terms of concerns, I can't think of any that are coming to mind."
Kerry also said "common sense" dictates that last week's attack in Ottawa was an act of terror, but that it will ultimately be for Canadian law enforcement to make a final determination.
Kerry said he didn't want to prejudice the ongoing police investigation, but he said the nature of the events speaks for itself.
"Clearly anybody who walks up in a premeditated way with a rifle and attacks somebody in uniform and then purposefully goes to a parliament is committing, by common sense standards, a terrorist act."
Baird echoed that "common sense" characterization, reiterating the view that the Conservative government has taken on the attack since last Wednesday when Prime Minister Stephen Harper linked the Ottawa shooting to terrorism.
Earlier, joined by Baird, Kerry placed a wreath at the National War Memorial.
The two then sat down to discuss the threat posed by Islamic State of Iraq and the Levant (ISIL), the situation in Ukraine, border management and North American energy co-operation.
"Both minister Baird and secretary Kerry discussed in detail the challenges facing Iraq and Syria from ISIL and what we can do to better co-ordinate our efforts," said a statement from Baird's office.
Canada has contributed six CF-18 fighter jets to the U.S.-led coalition to combat ISIL.
Baird raised the Keystone XL pipeline project, which Kerry's department is reviewing. Repeated delays in approving the line have caused friction between Canada and the U.S. But Kerry had nothing new to say on the status of the project.
Canadian officials quietly hope Congress may force Kerry and the White House to approve the project.
Kerry ended his whirlwind day in Ottawa with a late afternoon meeting with Harper in his Centre Block office on Parliament Hill, not far from where the armed man who shot Cpl. Nathan Cirillo was killed in a gunfight with security.
Harper, just back from Cirillo's funeral, welcomed Kerry on a "sad day" for Canada, and thanked him for the solidarity shown by the U.S.
Kerry offered the condolences of the American people to Canada on behalf of President Barack Obama.
And he thanked Canada for "standing up against terrorism."
Also on HuffPost