Boston Blast Leaves Unanswered Questions, Heightened Alerts [VIDEO/AUDIO]

A pair of bombings near the finish line of the Boston Marathon this afternoon has left at least two people dead - including a reported 8-year-old child, more than 100 injured, and a continued search for the responsible person(s).

The blasts went off at about 2:50 p.m. in the densely populated downtown section of the city, Copley Square, on Patriots Day, which is a usual joyous holiday for Bostonians, marked by the Boston Marathon and an annual Red Sox game.

"Today is a holiday in Massachusetts - Patriots' Day. It's a day that celebrates the free and fiercely independent spirit that this great American city of Boston has reflected from the earliest days of our nation," President Obama said, briefing the nation from the White House.

While speculation has been been rampant, the investigation and search for a suspect goes on this Monday evening.

"We still do not know who did this or why. And people shouldn't jump to conclusions before we have all the facts. But make no mistake, we will get to the bottom of this. And we will find out who did this; we'll find out why they did this. Any responsible individuals, any responsible groups will feel the full weight of justice," Obama said.

Blood Supply Stocked Up

New Jersey Reacts

While State Police Lt. Stephen Jones says there is no imminent threat in New Jersey, authorities have raised security as a precaution. The State Police bomb unit, aviation crews, tactical teams, and search and rescue assets have been pre-deployed.

NJ Transit has added extra patrols to trains and buses, while the Port Authority has heightened security at bridges, tunnels, and on PATH lines.

Meanwhile, Atlantic City Police has heightened their alert, but the city's 12 casinos remain open, and executives say they will not take on unusual security measures.

New Jersey authorities also placed a regional emergency medical technician network on a heightened state of readiness in case there is any incident in the state.

Moving Forward

The Associated Press contributed to this report.