If a serial rapist/murderer is able to repent, should he be saved from being hanged?

jus last year, there was this very famous guy in america, called Stanley Tookie Williams. He was a highly wanted criminal, one of the top black gangster in USA. He was convicted of murder and was put on the death row.

During teh time he was put on the death row, he was introduced to Buddhism. For the 10 long years while waiting for death, he wrote a lot of books. He helped alot of pple to quit gang and to become good pple. He gained popularity amongst the US pple. However, in Dec 2005, Williams was put to death by lethal shot. As the executioner was injecting the poison, his supporters were watching. when he died, they proclaimed that US had killed an innocent person.

Mr Arnie, governor of California, refused to revise the case, despite the god Wlliams had done, as Williams still denied he had commited the murder. Arnie felt that Wiliams showed no repentance and hence refused to reopen the case.

So many people were very angry, as his books had inspired many pple to do good.
Do check out teh following links or google his name to read more:

http://www.freerepublic.com/focus/f-news/1539508/posts
http://en.wikipedia.org/wiki/Stanley_Williams