Jocke is a character in Let The Right One In.
In the story he was the first victim of Eli. While he was getting home after a party he sees a young girl. He tries to help her but it only ended with him getting bitten in the neck and his neck getting broken.
His death sparked in his friends, especially Lacke whom he considers Jocke as his brother.
In Let Me In his name wasn't mention and was thought to be just a random jogger who came accross Abby