Anchored by Jake Tapper, The Lead airs at 4 p.m. ET on CNN.
Fmr. national security adviser Stephen Hadley, and the latest on the crisis in Ukraine.
Barely more than 24 hours ago, three of the people in the Boston Marathon's cheerful crowd were forever silenced, including 8-year-old Martin Richard. We now know more than 170 others, aged 2 to 71, are recovering from the physical wounds of these horrifying blasts.
"Severe trauma in lower extremities that was beyond salvation, so I would consider them almost automatic amputees, we just completed what the bomb had done," said Dr. George Velmahos, of Massachusetts General Hospital.
And the bombs, we now know, were loaded with shrapnel for maximum destruction.
"There is no question that some of these devices were, some of these objects were planted in the device for the purpose of being exploded forward when the bomb went off, so these are small – they are about two to three millimeters in diameter. And we have also removed over a dozen small carpenter-type nails from one patient," said Dr. Ron Walls, of Brigham and Women's Hospital.
The country is struggling to cope with the emotional aftermath.
"It's obviously an extremely sad day for all of us, but even more so for patients and relatives," said Velmahos. "Obviously they are shattered by the events,"
Since Monday's attack, details are emerging, namely that it was a terrorist attack, and that answers are still being sought.
"This was a heinous and cowardly act. And given what we now know about what took place, the FBI is investigating it is an act of terror," said President Obama.
"It was a terrorist attack of some sort. Now, again, until we know who or why, I don't think we can further define it," said Speaker John Boehner, R-Ohio.
No domestic or international group has claimed responsibility for this attack. But officials pledge to find out who is to blame as quickly as possible.
"We will find this person, trust me," said Thomas J. Nee, of the Boston Police. "And we will bring them to justice the American way, not the uncivilized way that they reap the carnage on us."