Welcome to the forum, Johnnelson! Hope you enjoy your stay here!
I can see where you're coming from on this question, sort of. When people kill, usually it's because they've forgotten to regard other people as people, and instead see them as subservient to some other end. But I wouldn't argue that they aren't feeling enough, but rather that they're letting their feelings - their passions - override their respect for others. When people kill, it is rarely because they're unfeeling; it's more often because they are angry, jealous, resentful, greedy... it's because they have some good end in mind, but are led to evil means to get it.
Regarding guns. Ultimately the gun rights defenders are right that the ultimate source of the problem is not in the gun but in the human heart. Guns are not a problem in themselves, but they're a multiplier effect for problems that already exist. Any disorders, any passions in the society - guns will make worse. Guns make the criminal drug culture worse; they make mental health problems more dangerous; they make domestic disputes more dangerous; they make anti-social behaviour more costly in terms of human life; they add an unstable element to general social distrust.