I recall reading a sutta in which the Buddha rises from meditation and says that while he was meditating, it occurred to him: Is it possible for a king to rule righteously without killing? If anyone knows the text I am talking about, it would be much appreciated.
What you are referring to comes from the Discourses of the Sutta Pitaka, and can be found within the book The Connected Discourses of The Buddha; A New Translation of the Samyutta Nikaya by Bhikku Bodhi, Vol. 1, pg 209.
"On one occasion the Blessed One was dwelling among the Kosalans in a small forest hut in the Himalayan region. Then when the Blessed One was alone in seclusion, a reflection arose in his mind thus: 'Is it possible to exercise rulership righteously: without killing and without instigating others to kill, without confiscating and without instigating others to confiscate, without sorrowing and without causing sorrow?' "
Try to read the "Cakkavatti Sihanada Sutta" - D26. It is the Discourse on the Lion-roar of the Wheel-turner.
The Supreme Buddha once explained... sometimes a person is born to the world with 32 bodily characteristics that a Buddha has. That person is known as a Sakviti Raja (a universal monarch). Even though the universal ruler also has the great 32 bodily characteristics, he could be a Prutakjana (one who has not come into Dhamma) person who has the propensity to be born in low-level worlds. Once he became the universal monarch, he rules the world or the Chakkavatti Rājjyaya (ChakkavattiKingdom) with great moral qualities. As a result of this, he gained great merits and will be reborn in heaven. However, if he is still in the Prutakjana state, he can get a birth in one of the four low-level worlds at the end of his lifetime in heaven. On the other hand, a noble disciple of Tathāgata (the Supreme Buddha) even with many difficulties in his life as a human will overcome the Prutakjana state. This results in his rebirth in same divine worlds as the Universal King was born. Thus, he overcomes the birth in these low-level worlds after his lifetime as that poor person. This example clearly shows us how the possibility of a normal being to be born in Hell, Animal, Preta, or Asura worlds.