Detectives investigating the disappearance of Sierra LaMar secretly placed a GPS device on a red Jetta belonging to their chief suspect Antolin Garcia-Torres as they carefully watched his every move for two month, hoping he would lead them to the missing California teenager. Investigators had questioned him several times as they collected evidence and interviewed witnesses, building a case against the alleged murderer.

On Tuesday, Santa Clara County Sheriff Laurie Smith explained why detectives arrested the 21-year-old on Monday, explaining why they are charging Garcia-Torres with murder, even without finding a body.

Smith said that investigators had discovered his DNA on her clothing in her bag that was discovered in a field two days after she disappeared, reported San Jose Mercury News. The crime lab also matched DNA from LaMar with items found in Garcia-Torres' vehicle that was confiscated in April.

Garcia-Torres and LaMar did not have any prior relationship of any kind. Smith called these the worst type of abductions because most victims are murdered within only hours.

We believe this is the worst type of crime, a stranger abduction of a young girl, the sheriff said at a news conference attended by Sierra's family, reported the Associated Press.

Mariene LaMar, Sierra's mother, had difficulty believing the outcome.

As a mother I'm hopeful, she said reported the San Jose Mercury News. Her body has not been found and that gives us hope.

She pleaded with Garcia-Torres to give them closure to the case.

Lead us to Sierra, and end this nightmare, she said.

Garcia-Torres' family believes they have the long wrong.

It's not him, Lucero Garcia, Antoloin's sister.

His mother, Laura Torres, said the family was well aware he was being watch by authorities. He reportedly told his mother that he never met LaMar nor did he ever have any contact with her, reported San Jose Mercury News.

Police officials investigating the disappearance worked in conjunction with the FBI to profile the suspect and gather DNA and circumstantial evidence. Garcia-Torres, 21, was arrested around 6 p.m. in a Safeway store in Morgan Hill, Calif. and booked in Santa Clara County Jail on one count of murder and one count kidnapping on Monday, reported the Associated Press.

We believe we have probable cause that he committed the kidnapping and murder of Sierra LaMar, said Santa Clara County Sheriff Laurie Smith.

Volunteers began mobilizing to find LaMar since she was first reported missing. Some refused to believe that she had been killed.

I'm glad they have a lead, said Karah Silacci, 38, of Gilroy. Silacci had volunteered on several searches for Sierra based from Burnett Middle School in Morgan Hill, reported the San Jose Mercury News. But I'm refusing to listen to the murder part.

Smith told reporters that the officers investigating the LaMar's disappearance have a lot of physical evidence to convict Garcia-Torres. She said that the main concern of her office is the protecting the public. We don't want to see anyone else hurt or any other little girls taken, she said reported the San Jose Mercury News.

Police suspected Garcia-Torres in LaMar's kidnapping for some time and had him under surveillance. Smith, however, did not elaborate any further on the operation.

However, police have not recovered the body of LaMar. Smith urged residents not to give up the search.

We ask that the public continue to look, and find Sierra for us, she said.

Police reportedly questioned Garcia-Torres for two hours trying to find the location of the missing teenager, reported KTVU. However, he has not given up any information.

Mac Klaas had been organizing volunteer searches since LaMar disappeared. His daughter, Polly, vanished in 1993 from his Petaluma, Calif. home. He speculated that after enduring the past two months without their daughter the family is possibly at the point where there won't be anything left to be afraid of, he said reported the San Jose Mercury News.

Smith also acknowledged that this is an extremely difficult time for the LaMar family. She asked that the media let them grieve and be left alone.

We've been communicating all along with the family and keeping updated on everything that we've been doing, Sheriff Smith said, reported KRON. The family has been cooperative. It's a very, very difficult time for them.

Klaas said he will continue to organize searches until LaMar's body is recovered, with a new search taking place on Wednesday, in hopes of still finding Sierra alive.

LaMar mysteriously vanished on March 18 walking back home from school. The day after she disappeared, investigators discovered her cellphone a few blocks east of her school bus. The next day, her pink bag was found containing a folded shirt and a pair of pants.

Over the past two months, there have been little details and little developments in the case. Ten days after LaMar disappeared, Smith's office removed her name from the missing person list, suggesting they were expected to find her dead.

As difficult as it is, and as much as you want your child home and safe, you need a resolution. You need to know. There are far too many cases unsolved or cold that leave people in limbo from which they're unable to move forward, Klaas said. Imagine what it's like, he said, to be told day after day that there's no real news? You get to the point you just need news. You need to know where is my child?