I think we have to recall that when tragedy occurs on a giant scale, like an earthquake that takes out a region of a foreign land, or as years ago when Katrina devastated parts of the United States, that there are people who will invoke God as the cause.
Perhaps we might realize that since God has told us He does not change and is the same as yesterday, today and forever, that the reason some may think today's God isn't the vengeful one we read of in the OT, is because people like those aforementioned one's aren't considered to be adding to the New Testament texts the actions of God, as they see it, and as was done in the Old Testament.
God sent the global flood. (The Book of Genesis chapter 6)
God destroyed Sodom and Gomorrah, (Genesis 18) out of vengeance for the sins committed there. Just two examples that tell us, while the new covenant reconciles us to God, God is still the same Holy Spirit "he" was in the old covenant. Only now when those aforementioned types state that the devastation that occurred on a mass scale was God's vengeance for whatever sin they name, those people are often mocked, even by Christians, and are dismissed as kooks. Even by television pastors of the fundamentalist type.
That's what can lead to people thinking there are two different God's referred to in the two covenants. When Christians say, no it isn't possible that Katrina was God's wrath for these sins.... It leads people to ask the question: then why was God the one responsible for the devastation of the first born of every Egyptian house? (The Book of Exodus chapter 11)
Some Christians will deny all that. While others will defend God saying, He's God. He can do whatever He likes with his creation. And those to positions in and of themselves put Christians at odds with the question asked early on in a different thread. "Is God a moral monster?"
If we did as God did to our enemies, would we be considered to be in Christ?
I know, "It's a mystery."
No, it's in the Bible.
God loves us.