Los Angeles – After an armed robbery in which the dog sitter of the American pop star Lady Gaga (36) was killed, one of the perpetrators has to go to prison for a long time. The 20-year-old was sentenced to 21 years in prison, US media reported on Monday. The man committed a “cruel and violent act,” the Los Angeles Times said in a statement from the Los Angeles prosecutor’s office. According to authorities, the perpetrator pleaded guilty to attempted murder.