According the official website for Shigofumi, the third episode that was aired January 16 was "altered in light of recent circumstances in the society at large". It also includes an apology for the lack of advance notice on the change, and asks on behalf the staff and cast for the audience's understanding on the matter.

Shigofumi: Stories of Last Letter is the story of a girl who delivers the last letter from the dead to those left behind. In the third episode entitled "Friends", the story focuses on three friends after one commits suicide. The father of the dead boy later enters the friends classroom and violently demands and explanation for his sons death.

With the lack of detail on behalf of the website and the recent alterations or preemptions of anime series such as School Days, Higurashi no Naku Koro Ni Kai, and Kodomo no Jikan, fans have been left to debate about current criminal events as the reason. Possibly the 18-year-old boy's alleged murders of his mother, brother, and sister on January 9, or the shotgun rampage that left three people, including the suspected shooter, dead on December 14 is the need for the alteration.

source: ANN