Speaking from Paris on American television on Sunday, Attorney General Eric H. Holder Jr. said the United States had yet to determine whether the Islamic State, Al Qaeda in the Arabian Peninsula or another terror organization was behind the Paris attacks. “At this point, we don’t have any credible information that would allow us to make a determination as to which organization was responsible,” Mr. Holder said on ABC’s “This Week.” Mr. Holder and a top homeland security official were in Paris on Sunday to meet with their counterparts.

Islamic State and Al Qaeda in Yemen, which use a similar black flag emblazoned with the Islamic declaration of faith, share the same commitment to violence but have disagreed on points of jihadist doctrine and compete for followers and funds in the Middle East and also in Europe.

The Islamic State split from Al Qaeda last year after years of ideological bickering, making their apparent coordination in France — or at least the coordination of people acting in their name — the only known case of cooperation to carry out such a high-profile assault.

The video, which was posted on Twitter and authenticated by a former lawyer of Mr. Coulibaly’s, a French citizen of African descent, opens with scenes of him doing pull-ups and push-ups at a training ground, as well as shots of his assembled arsenal of automatic weapons. The screen goes black, and a title appears: “A Soldier of the Caliphate.”