I've lost 115 reputation points because the user who had cast votes to my questions and answers has been removed.

I can see it impacted also other users, losing even 400 points.

Reputation points are rewards for users contributions to this site and deleting points from my reputation discourages me from further contributions, unless the votes has been cast in an unfair way. I've read the site is prepared for such behaviors and thus votes of deleted users are not deleted unless the deleted user is or ever was involved in voting fraud.

Does it mean the deleted user was involved in voting fraud?