1)
Why did he tear his garments?
1.
'Rashi' (Divrei ha'Yamim II, 34:19): He heard "Hashem will take you and your king that you put upon yourself [to exile]" (Devarim 28:36). He expounded, "that you put upon yourself" [refers to himself] - the nation made him king. It was not via a Navi according to Hashem's word.
2.
Radak (from Yuma 52b): The Sefer was rolled to the curse "Hashem will take you and your king
