SAN JOSE, Calif. -- A 21-year-old man in custody was linked to the kidnapping and murder of a missing teenager by DNA evidence found in her bag, authorities said Tuesday. Santa Clara County Sheriff Laurie Smith said Antolin Garcia-Torres's DNA was found inside a bag belonging to Sierra LaMar. Sierra's DNA was also found on unspecified property belonging to Garcia-Torres, according to sheriff's officials. Smith said it appeared to be a random act of violence. "We believe this is the worst kind of crime, a stranger abducting a young girl," she said at a news conference attended by Sierra's family. Garcia-Torres was arrested Monday on suspicion of murder and kidnapping of Sierra, whose disappearance more than two months ago prompted hundreds of volunteers to turn out for organized searches. Sierra hadn't been seen or heard from since she left her home in Morgan Hill to go to school on March 16. Authorities believe she was kidnapped while walking to a school bus stop. Smith said Garcia-Torres had been under 24-hour surveillance since March 28 and that evidence also linked him to at least one assault in March 2009. Authorities identified other suspects during the course of the investigation and also put them under surveillance before focusing on Garcia-Torres, Smith said. Garcia-Torres's DNA had been in a law enforcement database following his arrest on suspicion of felony assault, according to sheriff's officials. They did not provide details about that arrest. Volunteers and ...