Most happiness to as many as possible

We discussed this in my philosophy class the other day. Would the best thing be, if as many people as possible were as happy as they could get? Even if some people would get hurt in the process?
For example, what if you killed someone against the persons will, and gave all the persons organs to some who really needed them? The person whose organs you took propably wouldn’t be happy about it, but it would make a lot more people happy. Would it be worth it to take the happiness from one person if you could give happiness to maybe 10 more?
Of course you would never do this, but i find the idea very interresting. What do you think?