Exodus 2:12

And he looked this way and that way, and when he saw that there was no man, he slew the Egyptian, and hid him in the sand.

Cross-references

Exodus 2:17 shows Moses again intervening against injustice — rescuing shepherds — paralleling his protective instinct.

Acts 7:24-26 expands on Moses' killing, revealing his expectation that God was using him to rescue Israel.