As someone who studies international security, I was asked then about 9/11, and today I have been asked about the Boston Marathon. Some things seem quite familiar. Others are new. Still others are a puzzle. But there are also some fundamental truths.

The last time I had to talk about terrorism and Boston was 9/11. There was no Facebook to help assure friends and colleagues, and I did not own a cell phone, let alone a smart phone. But the media called. The Al Qaeda operatives had boarded their planes at Boston Logan Airport, the airport I use more than 100 times a year.

Most of us will be tempted to treat each new fact as evidence for a particular conclusion. But there will be many facts, and different facts will point in different directions — all at the same time.

On both 9/11 and yesterday, some early reports turned out to be misleading or just plain wrong. An earlier report that the John F. Kennedy Presidential Library was the site of an attack is a case in point. There was no attack at the library. It was, instead, an electrical fire. It was an honest mistake, and there is no avoiding those kinds of errors. The key here is not blame, but patience. In 48 hours, law enforcement and intelligence officials will have a wealth of information, and we will know a lot more about what took place.

That brings us to what is different. Today, investigators have access to data that, in some cases, did not even exist on 9/11. Cell phone tower transmission data, surveillance video, iPhone photos from a picture-taking crowd celebrating at the finish line. That, together with a scouring of telephone and email communications across the globe, will help rule out and rule in potential suspects.

And some things are a puzzle. For example, why did the bombs go off so long after the winners crossed the finish line? Is it a sign of incompetence, good defense by the government, or some unknown motive? Is the timing tied to Patriot’s Day or the U.S. tax deadline or both or neither? Is the perpetrator of foreign or domestic origin and motivation?

Here again, it’s best to be patient. Most of us will be tempted to treat each new fact as evidence for a particular conclusion. But there will be many facts, and different facts will point in different directions — all at the same time. Reports that there were multiple explosives set for near-simultaneous detonation might suggest organizational sophistication. Yet at the same time, the relatively low-grade of the reported explosive (non-military) and the late timing could suggest the opposite.

There are news reports that a foreign student is being interviewed by the police (traditionally, not a very strong indicator of anything at all) even as most experts (myself included) think that a decentralized Al Qaeda is more focused on regional goals in Syria, Yemen, and elsewhere and not on the U.S. homeland.

So there is a lot we do not yet know at this moment.