A day after twin explosions killed three and maimed dozens at the Boston Marathon finish line, we find ourselves waking up in a much-changed city. Gov. Deval Patrick says this morning expect major delays, possible police searches of bags on subways and access to some buildings closed to the public in the areas surrounding Copley. At this point law enforcement officials either have very few leads or are keeping key information close to their chest.

Nicole Bates, from Washington, D.C., was rushing away from the scene.

"I had just finished the marathon and had left the finish area," Bates said. "I was about two blocks away facing the finish line, heard a big explosion, things rattled around, and I saw a puff of smoke near the finish line at the library. I wasn't sure what it was, I was hoping it wasn't anything bad, but it sounds like it may be at this point. Just wishing the best for all the runners. It's such an incredible day and such a shame that somebody would do this."

"This is a shame," she said. "The city shuts down for this. It's a celebration. Twenty-six point-two miles of everybody cheering you on being a community and somebody just comes and tries to destroy it. It's ridiculous."

Glynn and Paula Rebecki of Chicago also heard the explosion:

"We were just about .2 miles from the finish, made the turn over the bridge, made the left, coming down, and then you heard the boom," Glynn Rebecki said. "Then you heard the second boom. And then the police came out and just pushed everybody back."

At 2:30 p.m. on Patriot's Day, Boston Globe photographer John Tlumacki was trying to capture the thrill of runners at least finishing the race and captured the explosions instead.

Boston Police Commissioner Ed Davis described the crude but deadly blast.

"This is a very powerful blast, there were serious, serious injuries," he said.

Davis said police were searching bags and knapsacks left behind by people fleeing the scene to try to find out who may have planted the devices.

"We are in the process of going through all of the abandoned property that was discarded in those places," Davis said. "We've pretty much cleared the Boylston Street area. There are no further devices that we've located at this point in time, but we are getting reports from various places about suspicious packages. That's perfectly understandable in this situation. I'm not prepared to say that we are at ease at this point in time. We are still very actively pursuing every lead that we have."

FBI Special Agent in Charge Richard DesLauriers now in charge of the overall investigation said this is what we know so far.

"The most important fact that I want to convey to everybody this evening has already been mentioned by Gov. Patrick the FBI is taking the lead in this investigation," he said. "It is asserting federal jurisdiction. It will do so through the Boston Joint Terrorism Task Force, members of which are comprised by all the law enforcement agencies represented at the podium. This will be a combined federal, state and local effort. It will be an ongoing investigation. It is a criminal investigation that is a potential terrorist investigation."

And this is what we don't know: Who did this and why?

"I want to stress one thing," Davis said. "There is no suspect at Brigham and Women's Hospital. There are people we are talking to, but there is no suspect at Brigham and Women's Hospital, as has been widely reported in the press. I'd like to fix that right now."

There were three major press conferences on Monday, but DesLauriers and other officials were deliberately vague about the details of this crime and the subsequent investigation.

"I'm not going to comment on specific investigative leads that are ongoing right now," he said. "I'm not at liberty to. But there is investigative activity ongoing right now … it is a very active and fluid investigation at this time. All resources, federal, state and local, are being brought to bear … again, I'm not going to comment on the investigation right now in terms of the number of explosives that were found at the location."

I’m in Copley Square, which is still wrapped in yellow tape and blocked off by police barriers. “A crime scene” is how the FBI and the Boston Police describe this area where the two bombs went off. But with dozens of FBI and ATF agents present, it feels more like the lingering shock experienced in the days after 9/11 than anything you may have seen on "Law and Order." Officials have not designated this crime as an act of terrorism. Yet people felt they were terrorized by the twin explosions.

"As you all know, this community has been dealing with a horrific event today two explosions on Boylston Street near the finish line of today's Boston Marathon," Patrick said. "Over 100 people were injured, some gravely. We are not ready yet to confirm the details of those injuries."

At this time, police count three fatalities, among them an eight-year-old.

The attack on Patriots Day drowned out the names of the winners of the Boston Marathon and has forced a new normal on the city at least for the next few days. Bags will be searched, subways may run slower, as investigators will try to determine who was responsible for this crime; for this terror.