Carlisle was the son of a minister and his father was very involved in a huge fight against vampires in London. There were incredible battles between the religious folks and the vampires, and in one of them, Carlisle was wounded very badly by a vampire.
As he was lying in the street bleeding, he realized that there was some chance that he would be come a vampire and he knew that his father would kill him if he transformed. So he hid himself in a cellar to allow the transformation to take place.
He actually tried very hard to kill himself as he hated what he had become, but was completely unsuccessful. He eventually learned that he could actually feed on animals and so became more comfortable with his condition and accepted it.
Carlisle Cullen was the son of an Anglican pastor, born in 1640s London, England, during a time of religious upheaval. His father and other pastors hunted creatures such as witches, werewolves, and vampires, often mistaking humans for them. As his father grew older, Carlisle assumed his role. One night, he was attacked by a vampire and left to die on the streets. Knowing he would be rejected by society, he hid himself and silently endured the painful transformation, emerging as a vampire. Horrified by what he had become, he tried killing himself many different ways, but all failed due to his power. One night, unable to endure hunger any longer, he fed on some passing deer. Subsequently realizing he could avoid feeding on humans, he committed himself to resisting his blood lust and to becoming a doctor.