That's what Elisha said to his servant, Gehazi. And when Elisha speaks, he speaks for God.
So God gave Gehazi and all of his descendants leprosy. He had a reason, of course. He always has a reason. But it really doesn't matter what it was, does it? The punishment was unjustified no matter what the crime may have been.
But I suppose I should tell the story anyway.
It all starts out well enough, with Elisha curing a man named Naaman of leprosy by having him wash seven times in the Jordan River.
Then went he down, and dipped himself seven times in Jordan, according to the saying of the man of God: and his flesh came again like unto the flesh of a little child, and he was clean. 2 Kings 5:14
Naaman offered to pay Elisha for the cure, but Elisha refused his offer. Gehazi, Elisha's servant, thought a payment was reasonable, though, so he went to talk to Naaman about it.
Gehazi told Naaman that Elisha wanted a talent of silver (about 35 kg) and two sets of clothing.
My master hath sent me, saying, Behold, even now there be come to me from mount Ephraim two young men of the sons of the prophets: give them, I pray thee, a talent of silver, and two changes of garments. 2 Kings 5:22
Naaman thought that was reasonable enough, so he gave him the silver and clothes.
When Gehazi returned, Elisha asked him where he went, and he said, "thy servant went no whither." ("I didn't go anywhere.")
But Elisha, like God, knows pretty much everything, so he knew Gehazi was lying about that. So Elisha cursed Gehazi and all of his descendants with leprosy.
The leprosy therefore of Naaman shall cleave unto thee, and unto thy seed for ever. And he went out from his presence a leper as white as snow. 2 Kings 5:27
The Bible doesn't say what became of Gehazi, whether he died because of the leprosy or not. (Although he does show up a few chapters later talking to a king, which would be unlikely for a person who was "unclean" because of leprosy.) But in those days, giving someone leprosy would be a death sentence.
Giving someone leprosy for lying is cruel and unjust; giving leprosy to the unborn future descendants of such a person is even more so. No reasonable person could think otherwise.
But did God kill anyone in this little Bible episode? Well, if God gave Gehazi and all his descendants leprosy, then some of them died because of it. But the Bible doesn't say whether Gehazi had any children, and it doesn't say what happened to Gehazi. And it is possible that "leprosy" in the Bible refers to some other type of skin disease.
So I'm not going to include this in God's killings, although it is a good story to remember. Bible believers believe that God gave Gehazi and all of his descendants some type of nasty skin disease.
Only a nasty God would do something like that.