Police in Los Angeles are trying to track down a stalker who has informed celebrity tattoo artist Kat Von D he's planning a killing spree after she obtained a restraining order against him. The reality TV star, who has dated Sandra Bullock's ex Jesse James and electronic dance music star Deadmau5, has told cops she fears for her life and the lives of others after receiving online death threats from Michael Nunn. Von D was granted a restraining order against Nunn in 2012 and now the Iowan insists his life is over and he's planning to go out in a blaze of glory. In a tweet he sent out on 4 June (14), Nunn wrote, "You have to understand, Kat, my life is over because of you. Therefore, what would my only reason for living be? Revenge." He then threatened to "go Columbine in Los Angeles... in a few weeks", referring to the deadly 1999 Columbine school massacre in Colorado. Nunn added, "Get it through your f**king head!! Lose the game or watch people die!... Your (sic) running out of time and I'm not running out of anger and determination." Police are taking the threat seriously and, according to TMZ.com, officials have launched a search to track him down.