Coulibaly, who is accused of killing a French police officer and killing four more people at a kosher grocery store, was described as a logistics expert in charge of accumulating weapons and arms for the prison break plot.
Records show when he was arrested in 2010, police found "a huge cache of high-caliber arms," including 240 cartridges for machine guns for "the specific goal of seriously hurting people through intimidation or terror acts."
Police also found computers with security and encryption and recipes for poison purportedly capable of killing a million people.
Cherif Kouachi, accused of killing 12 people after attacking the Charlie Hebdo magazine last week with his brother, was implicated in the prison plot, but he denied involvement and was not jailed for that.
Kouachi and Coulibaly had a mentor in common, a radical named Djamel Beghal. Once known as al Qaeda's premiere European recruiter, Beghal was convicted of conspiring to attack the U.S. Embassy in Paris.
Kouachi had met Beghal in prison, and once they were freed, he would visit him with Coulibaly, bringing Beghal food and money -- and sometimes spending days at his apartment.
Court documents detail how Kouachi and Coulibaly plotted together, hiding their conversations by using code names over disposable cell phones.
But what about Beghal? Does he have any direct connection to last week's attacks? And what happened to him?
Photos show connections
Beghal was first arrested in Dubai in 2001 for his role in the embassy plot. He was in custody until his trial and conviction in 2005, then released on house arrest in 2009.
After Beghal's release, French authorities collected more than 45,000 pages of wire transcripts and surveillance images of him, including when he was under house arrest.
The images include a 2010 photo of Beghal with Cherif Kouachi and two other men, in a park. And a second photo, also taken in 2010, is of Beghal with Coulibaly, who visited the recruiter in Cantal, France, with Boumeddiene. A Western intelligence source verified the authenticity of the images obtained by CNN.
Beghal's time out of prison didn't last long.
In 2010, he was arrested and charged with involvement in same prison-break plot that landed Coulibaly in prison. He was sentenced to 12 years in prison and remains behind bars.
Lengthy history with al Qaeda
Beghal's ties to al Qaeda stretch back before the 9/11 attacks in the United States against the World Trade Center and the Pentagon, the source said.
In November 2000, Beghal traveled to Afghanistan for eight months, also visiting Pakistan.
According to court records, he was put in charge of the plot to blow up the U.S. Embassy in Paris -- an attack eerily similar to the 1998 attacks against U.S. Embassies in Kenya and Tanzania.
The Western intelligence source says Beghal was given instructions to go to Dubai and then Morocco, where he would lose his old passport and get a new one. He was then instructed to travel to Spain where he would be given the equivalent of $60,000 to carry out the Paris attack on the U.S. Embassy. But Begahl was stopped and questioned as he passed through Dubai. According to the Western intelligence source, he confessed during interrogation to the planned attack on the embassy. He was ultimately convicted in a French court.
U.S. authorities never brought charges against the French-Algerian as they did other al Qaeda operatives involved in 1998 attacks on U.S. Embassies in East Africa.
Beghal's mentor was Finsbury Park mosque cleric Abu Hamza al-Masri, convicted just last week on terrorism charges and sentenced to life
by a federal judge in New York.
Abu Hamza is believed to have radicalized and influenced convicted terrorists shoe-bomber Richard Reid and 9/11's Zacarias Moussaoui.
The source says Beghal later took the name Abu Hamza out of respect for his mentor.