Az Yashir

When the Jews started singing Az Yashir the angels got so happy that they started singing also. Hashem silenced them because they were singing really when they had no right to sing. Hashem asked them why they were singing when some of Hashem's creations got killed. This tells us a little about Hashem. He only killed the Egyptians because they had enslaved the Hebrews for 210 years but not willingly. Whenever someone has to die young or has to be destroyed Hashem does it but because it needs to be done, not because He is cruel.