What does "that" in "after that" refer to in this āyah and to whom is it addressed?

Imām Ibn al-Jawzī (d. 597/1201) summarized the scholars' opinions in his book "Zād al-Masīr" as follows:

1. It refers to the resurrection of the dead, and the address is to all the Children of Israel. [Mentioned by the commentators]
2. It refers to the speech of the murdered person, and the address is to the killer. [Mentioned by the commentators]
3. It refers to the signs that have been mentioned such as the transformation into apes and swine, the raising of the mountain, the gushing of water, and the resurrection of the murdered person. [Mentioned by al-Zajjāj]