No. One is murder and the other is killing. Killing can be justified.
Anything can be justified in one's own mind. I just did my taxes and made some outrageous deductions that I felt I could justify, the IRS may pass a different judgement however.
So you can support your justified killings in your own mind and not consider it the murder that I know it to be.
Consider the following:
"After five years on Louisiana's death row, Ryan Matthews received a second chance at life. He was exonerated last year with the help of DNA evidence.
"He was 17 years old at the time of his arrest and is borderline retarded," said Martha Kashickey, the public-education associate for the Innocence Project at Yeshiva University's law school in New York City.
"Post-conviction DNA testing on the mask the perpetrator left at the scene both exonerated Matthews and revealed the identity of the actual perpetrator," Kashickey said from New York City."
http://news.nationalgeographic.com/news/2005/04/0408_050408_tv_dnadeath.html
If this innocent man had been killed as you desire, it would certianly be murder, how could it be otherwise.
I reject the idea of killing/murder and God will have the final judgement on us all including you.