That's horrible.
"Romantic love" brings with it extreme emotions. There are many who simply cannot negotiate these when things in the relationship turn negative.
Imagine the scrambled state that must exist in the mind of an individual who would resort to such violence against someone who "meant so much".
Helen Fischer, a Biological Anthropologist, out of Rutgers University has done some interesting work on love and relationships and biology. She has scanned the brains of people who have just recently been dumped and found that three specific parts of the brain are highly activated (Ventral Tegmental and caudate nucleas and one other). These parts of the brain are also associated with drug addiction. Both drug addiction and the longing for love have similar characteristics (e.g., intense energy, intense focus, intense motivation and the willingness to risk it all to win lifes greatest prize--drugs or love). Thus, just as the drug addict uses intense energy, focus and motivation to obtain the drug, someone who has been dumped may use the same intense energy, focus and motivation to "obtain" their ex..........sometimes with drastic consequences.
The issue is that most of us do not come murder our ex-partners. So, what is the difference? Perhaps these areas of the brain are more activated in some people? Or, perhaps these people do not have good coping mechanisms to deal with a break-up? Or, perhaps an innate temperament or personality style, mixed with biology, is the reason for it.
"I have come to think that romantic love is a drive, a basic mating drive. Romantic love enables you to focus your mating energy on just one at a time, conserve your mating energy, and start the mating process with this single individual. I've also come to believe that romantic love is an addiction: a perfectly wonderful addiction when it's going well, and a perfectly horrible addiction when it's going poorly. The god of love lives in a state of need. It is a need. It is an urge. It is a homeostatic imbalance. Like hunger and thirst, it's almost impossible to stamp out. It has all of the characteristics of addiction. You focus on the person, you obsessively think about them, you crave them, you distort reality, your willingness to take enormous risks to win this person. And it's got the three main characteristics of addiction: tolerance, you need to see them more, and more, and more; withdrawals; and last, relapse." Helen Fisher