Justifiable Death?

In the UK there is a case where a man was stabbed to death on a busy street in London during the daytime. When i first heard this i was pretty shocked but now the following news has been released about this individual.

"A man stabbed to death in Oxford Street this week was facing charges of raping a 16-year-old girl and pouring acid over her afterwards to hide the crime, police revealed yesterday."

I've always though that I had a small dose of compassion mixed with a large helping of ethics. I remember a discussion i had with my Spanish friend about when and if it was right to ever kill, going through the usual arguments of if you knew killing one person would save a million etc ( i.e new Hitler) anyhow we both came to the conclusion it was totally wrong to kill under any circumstance. But now after seeing so much violence and for want of a better word "$h1t", i shamefully feel a kind of "good riddance" to the guy that go killed, an almost another bad bug has been swept clean from our streets. Its a new kind of emotion and i think its probably best if i leave this place before i totally lose all my values by being numb to this hostile and violent environment i call home?

http://www.independent.co.uk/news/uk/crime/oxford-street-gang-murder-victim-faced-trial-for-rape-828291.html