4 who were burying all their firstborn, whom the LORD had struck down among them; for the LORD had brought judgment on their gods.

Read Numbers 33:4 Using Other Translations

For the Egyptians buried all their firstborn, which the LORD had smitten among them: upon their gods also the LORD executed judgments.
while the Egyptians were burying all their firstborn, whom the LORD had struck down among them. On their gods also the LORD executed judgments.
Meanwhile, the Egyptians were burying all their firstborn sons, whom the LORD had killed the night before. The LORD had defeated the gods of Egypt that night with great acts of judgment!