In the mindlessness of its evil, the 16th Street bombing was also the most heinous act of the era.

When In the early morning of Sunday, September 15, 1963.
Where The 16th Street Baptist Church in Birmingham, Alabama
What As children filed into the church for a worship service, 122 sticks of dynamite, with a time-delayed fuse, exploded outside the church basement
Who Four young girls –Addie Mae Collins (14), Denise McNair (11), Carole Robertson (14) and Cynthia Wesley (14) were killed by the blast. Other children were gravely injured. Later in the day two more young African-Americans were killed in shootings in the aftermath of the bombing. No arrests were made at the time of the bombing. The FBI later reopened the case.

In 1975, Robert Chambliss was convicted of four counts of murder in the case. In 2000, the case was again reopened and two other men were convicted: Bobby Frank Cherry and Thomas Blanton. Two other suspects died before being charged.
This is the New York Times account of the last of the convictions in the case.
http://www.nytimes.com/2002/05/23/us/38-years-later-last-of-suspects-is-convicted-in-church-bombing.html?scp=4&sq=Birmingham+bombing+convictions&st=nyt

There are many excellent books about the civil rights era. Here are four of particular note:
Carry Me Home by Diane McWhorter is a Pulitzer Prize-winning book about Birmingham that focuses on the bombings.
Eyes on the Prize by Juan Williams and Julian Bond, companion to a PBS documentary series
Parting the Waters by Taylor Branch is the first of a 3-part biography of Martin Luther King that goes up to 1963, the year of the bombings.
My Soul is Rested is an excellent history of the civil rights era by Howell Raines, a New York Times writer who also wrote a magazine piece about Birmingham on the 20th anniversary of the church bombings.
http://www.nytimes.com/1983/07/24/magazine/the-birmingham-bombing.html?scp=5&sq=Birmingham+Bombing+Howell+Raines&st=nyt