AUGSBURG, Germany (Reuters) - A 29-year-old car mechanic was sentenced to life in jail on Wednesday for sexually abusing and murdering a seven-year-old girl in a case that shocked Germany and led to calls for sex offenders to be kept in prison. Arnim Schreiner, a previously convicted sex offender, confessed that he kidnapped Natalie Astner on her way to school in September 1996, molested her and then killed her. Judge Hans-Reiner Schultz announced the sentence in a packed courthouse in the southern town of Augsburg. Natalie's grandfather Erich Kettner told reporters outside the courtroom: "Schreiner is still a dangerous man and he has to stay in jail until the day he dies. He is a ticking time bomb and will still be dangerous if he is released at age 60." Schreiner, who had described himself as a poor and lonely man suffering from depression, had testified he felt jilted by his girlfriend and rejected by the opposite sex. He said he decided to grab a child after waking up on September 20, 1996. Schreiner had been released early from jail after serving time for previous sexual assault convictions.