God directs us in the 10 Commandments not to kill, but the 10 Commandments are for us to follow. He Himself created life and He Himself may take it away.
God gives everyone plenty of chances before He acts. Read more closely. God is merciful and only acts as a last resort. Begin with Genesis and then onto Exodus; how many chances did he give to Pharaoh before he struck at the Egyptians? God gives life, and if He sees fit, He can take it away.
DISCLAIMER: Catholic Answers has turned over the archive to Catholic-Questions.org and no longer owns, manages, or moderates the forums. For additional apologetics resources please visit www.catholic.com.