More than 60 years ago, one of the most vicious acts of violence in American history was committed when an explosion ripped through the 16th Street Baptist Church in Birmingham, Ala., taking the lives of four young Black girls who were attending Sunday School and preparing to sing in their church choir.

The bombing that killed Addie Mae Collins, Cynthia Wesley, Carole Robertson, each 14, and Carol Denise McNair, 11 was described as "one of the most vicious and tragic crimes ever perpetrated against humanity” by Rev. Martin Luther King. The act of domestic terrorism was carried out by four Ku Klux Klansmen who placed 19 sticks of dynamite rigged to a timing device beneath the steps of the church.

One of the perpetrators, Robert Chambliss was arrested and tried with murder on Oct. 8, 1963, but was cleared on the murder charges and sentenced to six months in jail for having the dynamite and a $300 fine. Fourteen years later on Nov. 18, 1977, Chambliss was convicted of the crime. He was sentenced to life in prison and died in 1985. Two others, Thomas Blanton and Bobby Frank Cherry were convicted in 2001 and 2002, respectively. Blanton was sentenced to four consecutive life terms and died in prison in 2020. Cherry was sentenced to life but also died in prison in 2004.Another suspect who was never brought to trial, Herman Frank Cash, died in 1994.

During the mid-‘90s, the men were the subject of a reopened FBI investigation into the bombing in an attempt to finally discover the truth of what really took place. CBS' crime series FBI TRUE examines how authorities went about finding out the truth in a new episode titled, “The Birmingham Church Bombing: The Long Arc of Justice.”

Airing on Wednesday, Feb. 14 (10:00-11:00 PM, ET/PT) on CBS, and streaming on Paramount+, former agent Kristy Kottis speaks with Special Agents Bill Fleming and Ben Herren, and former U.S. attorney and Alabama Sen. Doug Jones about the bureau’s findings and the continual pursuit of justice decades later for the four girls.The story takes a look at the murderous intentions of each of the suspect, each members of the Ku Klux Klan, and how justice for the girls had been blocked for decades.

In the trailer for the episode, Kottis asked Fleming, Herren, and Jones about the results of previous investigations when Alabama.

“The investigation started in 1963. Do we get any convictions? At this point what happens?” Kottis asked.

“The bureau spent an incredible amount of resources but in those days, it was really only a five-year statute of limitations for civil rights deaths,” Jones answered. “So in 1968, there had been no indictments and J. Edgar Hoover closed the case. I think everybody had a really good idea about who committed this bombing. But there was just not enough that can be used in a court of law.”

“And you had an all-white jury, all-male, White jury, and they would have never been convicted,” Jones added.However, Jones, Fleming and Herren talk about how the case went from a long shot to getting convictions of the remaining two men using forensic evidence and witnesses who came forward to tell of the horrific plans they had kept to themselves for years.

Considered one of the most important events of the Civil Rights Movement, the impact of the vicious attack ultimately helped to garner more support  for the eventual  passage of the Civil Rights Act of 1964 by Congress.

Kimberly McNair Brock, the sister of Denise McNair, the youngest victim of the bombing, spoke about the long-lasting impact of the immense tragedy in an interview with BET.com.

“As kids growing up, It was always a part of our lives," McNair Brock said. “I would imagine from that point in my parents’ lives, in their world, everything changed because that was their only child.”

King, who eulogized Collins, McNair, and Wesley (a separate service was held for Carole Robertson) in a joint funeral, said the girls “did not die in vain.”

“They died between the sacred wall of the church of God, and they were discussing the eternal meaning of love,” King said.

Good night, sweet princesses. Good night, those who symbolize a new day,” King added. “And may the flight of angels take thee to thy eternal rest. God bless you.”

CBS' FBI TRUE  “The Birmingham Church Bombing: The Long Arc of Justice airs on Wednesday, Feb. 14 (10:00-11:00 PM, ET/PT) on CBS, and streamis on Paramount+.