A devastating bombing in Oslo, followed by an armed assault outside the city sparked another explosion--one of speculation over who was behind the attack. Such conjecture is axiomatic after such incidents—but until there is evidence to back it up—it is all just guessing. The instant analyses and “lessons learned” now spewing forth may not hold water once the facts are in.

No one—terrorism expert or man-in-the-street—will be surprised if the attacks are linked to Islamist terrorists. There are plenty reasons to believe Norway might be a target. An Al Qaeda cell was unmasked there last year. And just a few days ago, Norway indicted a radical Iraqi cleric Mullah Krekar, (founder of Ansar al-Islam) for making death threats against Norwegian officials.

But speculation adds little value to the hard work of fighting terrorists. Nor is it usually necessary in the wake of these kinds of attacks. Usually the perpetrators leave a lot of evidence. Even bombings leave a trail that can be traced. In the aftermath of the Oklahoma City bombing of the Murrah Federal Office Building, police quickly found the VIN plate of the vehicle that carried the bomb to its target.

So let’s not let speculation get too far out ahead of the investigation. After all, there’s a lot of hard work that needs doing.

Terrorists like to sow chaos and confusion with more chaos and confusion. Responders need to be worried about follow-on bombs or attacks that target them. Groups that perpetrate violence often plan a string of attacks. Officials need to be anticipating the next shoe that might fall. Finally, finding perpetrators is always easiest when the trail is fresh—so ensuring that evidence is properly protected, analyzed, and acted on is a priority.

There are many essential tasks to be done in the aftermath of a terrorist attack. Speculation is not one of them.

James Jay Carafano is director of The Heritage Foundation’s Allison Center for Foreign Policy Studies.