Going to Hell?

This might sound stupid but bare with me, as a catholic I'm scared to be a veterinary technician because one of the requirements in doing this is putting dogs down when no other option is available with the permission of the owner. My question is, do you think constantly putting animals down would be considered murder because I'm not really consenting with the animal (even though they can't talk) like what gives me the right to decide if an animal decides if it wants to go away in pain or not? I know the one agreeing to it is the owner but doing the act itself you take part in it. Idk just a thought.