Chang Ge was shooting to kill obliviously but I am less clear on Sun. I read it as he shot to kill also and the…
He is a master at archery so if he had wanted to, he could've shot to kill but instead he lowered his arrow on purpose to hit her in a less vital spot to hopefully incapacitate her so she would retreat from battle (in a sense protecting her) but didn't expect her to stand back up. That's why after he kept asking his friend how his archery skills were because he was worried that he shot too well and ended up hurting her.