"...I could tell he was still reluctant to donate his blood to the victims" This is how I would say it. "reluctant" makes it sound like he is there to help, just nervous to donate. "begrudged" is more like he is there and will help but really doesn't want to, possibly even hates that he is helping.

I agree with CJHepp: "reluctant" is the only normal way to say it. If you use begrudged or grudged, then it tells me that he honesty believed that the victims didn't deserve his blood. Begrudged carries a further sense of jealousy, as if he needed his own blood more than the shooting victims did. Even though the sentences are grammatically correct, the person appears to be a very, very selfish little man. "Reluctant" can suggest other reasons, eg. a dislike of needles, or a fear of giving blood.

yes i agree with you guys it's defently "...I could tell he was still reluctant to donate his blood to the victims