that's not a bad idea. I had been thinking only along the lines of a direct communication which, as YellowSubmarine
pointed out, is difficult for anatomical reasons.
Alternatively, we could develop a language based on symbols on a touchscreen or a set of cards you'd have to touch (that's something both species could do)
I don't think you can compare the killing of animals and humans with each other. Animals kill for food or territorial reasons (wich usually are about food, in the end). Humans often kill for fury, for greed and in order to completely extinct the others, not just their immediate opponents. That's something any other organism on this planet would consider totally unthinkable.