Fredo was reciting the Hail Mary just before he was killed in The Godfather Part II.
In the film’s climactic Lake Tahoe sequence, Fredo Corleone goes fishing with Al Neri while Michael watches from the shore. Fredo recites the Catholic prayer as part of his familiar fishing ritual: earlier in the film, he explains that saying the Hail Mary helps him catch fish. The ritual becomes ominous because Michael has secretly ordered Neri to kill him.
The Hail Mary is a central Catholic prayer addressed to the Virgin Mary. Its closing words ask her to pray for sinners “now and at the hour of our death,” giving the scene an especially stark connection to Fredo’s fate. The film cuts away from the boat as the shot is heard, so viewers do not see the killing directly. The scene is sometimes remembered as Fredo finishing the entire prayer, but the film clearly establishes that he is reciting the Hail Mary.