What happen when hawkeye tries to shoot to a character with shape change , and his shape change works, but there is another enemy in hawkeye line of fire?
Hawkeye attacks second character and goes on with his running shot , or he stops his attack?

Please quote the effects in question.

If the character he targets makes it's SC roll, then he can target another character (assuming there is one within range and LoF) from where he currently is. If there isn't another character for him to target with that attack, then he will not be able to Running Shot again.

When Shape change succeeds it let's the attacker choose another legal target if available. .

Shape Change: