Today's Situation Room:
Wolf Blitzer delivers the most important breaking news and political, international, and national security stories of the day. Tune to The Situation Room weekdays 5-7pm ET on CNN.
Gov. Patrick: No one in custody
CNN's Wolf Blitzer talks to Massachusetts Gov. Deval Patrick about the ongoing bombing investigation in Boston.
RELATED STORY: Sources: Possible suspect sought in Boston bombing
Obama: Gun lobby 'willfully lied'
President Obama criticized the NRA and a group of senators for blocking an expansion of background checks for gun sales.
RELATED STORY: Senate rejects expanded gun background checks
The medical effects of ricin
CNN's Sanjay Gupta explains ricin and how deadly the poison can be.
RELATED STORY: Ricin scare rattles Washington
Source: Bombs were in pressure cookers
CNN's Joe Johns looks at the nature of the explosives used in the Boston Marathon blasts.
Letter laced with ricin sent to Senate
A suspicious letter containing ricin, a poison, was addressed to a senator, according to sources. CNN's Dana Bash reports.
RELATED STORY: Ricin scare rattles Washington
Third victim was a B.U. grad student
CNN's Wolf Blitzer reports the third victim in the Boston Marathon attack was a Boston University graduate student.
RELATED STORY: Sadness, resolve as Boston comes to grips with deadly marathon bombing
Bombing victim's mom: Everyone loved her
Patty Campbell says Monday's terror attack in Boston doesn't make any sense. Her daughter, Krystle, died in the bombing.
RELATED STORY: 'Boston will overcome,' mayor vows amid bombing investigation
Boston Marathon terror attack analyzed
CNN's Tom Foreman takes a closer look at how and where Monday's terror attack in Boston occurred.
RELATED STORY: Boy, 8, one of 3 killed in bombings at Boston Marathon; scores wounded
Obama: We will get to the bottom of this
President Obama reiterated that investigators do not yet know who is behind the explosions in Boston.
RELATED STORY: Boy, 8, one of 3 killed in bombings at Boston Marathon; scores wounded
Watch Boston Marathon explosions
A photographer captured the two explosions at the Boston Marathon up close.
RELATED STORY: Boy, 8, one of 3 killed in bombings at Boston Marathon; scores wounded
About this Show
The Situation Room with Wolf Blitzer is the command center for breaking news, politics and extraordinary reports from around the world. Tune in weeknights from 5-7pm ET on CNN.
