Moses orders killings

Exodus 32:26 says, “Then Moses stood in the gate of the camp, and said, Who is on the LORD's side? let him come unto me. And all the sons of Levi gathered themselves together unto him.

32:27 And he said unto them, Thus saith the LORD God of Israel, Put every man his sword by his side, and go in and out from gate to gate throughout the camp, and slay every man his brother, and every man his companion, and every man his neighbor.

32:28 And the children of Levi did according to the word of Moses: and there fell of the people that day about three thousand men.”  I thought breaking the stone tablets was over reacting.  Killing about three thousand men is just plain crazy.  They must really fear Jehovah.  Isn’t it odd that for the people breaking a judgment (Exodus 20:3 “Thou shalt have no other gods before me”) Moses breaks another judgment (Exodus 20:13 “Thou shalt not kill.”)   Is god aware of all of these violations of his rules?  The funny thing is that all of the children of the men who worshipped these other gods will be punished by Jehovah. Exodus 20:5 “Thou shalt not bow down thyself to them, nor serve them: for I the LORD thy God am a jealous God, visiting the iniquity of the fathers upon the children unto the third and fourth generation of them that hate me”  Even Aaron.