ORANGE PARK, Fla. -- The body of little Somer Thompson has been found and identified. Now the job begins to find and catch her killer. Eyewitness News spent all day looking through the tactics and technology detectives will use to hunt this murderer down.

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VIDEO REPORT: Tracking Down Somer's Killer

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Clay County's sheriff confirmed Thursday that 7-year-old Somer Thompson's body was found Wednesday at a landfill on the Georgia-Florida line. They identified her based on her clothing and a birth mark.

Detectives are questioning sex offenders who live near Somer's home in Orange Park. That's just one method detectives will use to catch the killer.

The body was found in landfill. Investigators from the FBI and the Georgia Bureau of Investigation are going to spend the next several days sifting through the 225 tons of trash from Somer Thompson's neighborhood in Orange Park that trucks carried out of state Tuesday morning.

Forensics experts say investigators will likely try to get DNA evidence from her clothing, hands, fingernails and mouth and they would also check for DNA on the garbage found near her body.

“I believe the early discovery of the body is going to enhance our investigation,” Clay County Sheriff Rick Breseler said.

An Eyewitness News law enforcement source who oversees this type of investigation says Somer's killer is probably a sex offender who lives in or has close ties to Orange Park, Florida. The source said Somer was probably murdered within two hours of her kidnapping and her body was probably disposed of in a dumpster, both moves intended to prevent the killer from being caught.

The law enforcement expert believes the search Thursday at a vacant home and a dumpster near Somer's school is a very encouraging sign. Investigators say in front of the vacant home is where Somer was last seen.

State officials say 161 convicted sex offenders live within five miles of Somer’s home. If the FBI recovers a suspect's DNA, it will be compared against the sex offender database and a national database that contains over 7 million DNA profiles of convicted criminals.

“I fear for our community until we bring this person to justice,” Breseler said.

Somer disappeared while walking home from school in Orange Park, south of Jacksonville. The area is lined with apartments, so investigators will also be looking for surveillance video. Surveillance video from a nearby car wash led investigators to the man who abducted and killed 11-year-old Carlie Brucia in 2004.

Sources say investigators can use software developed by NASA to enhance surveillance pictures by as much as 200 percent so they get a clear image of the suspect and high-tech gadgets are often used to track a suspect’s movements and help build a case. If they can get a court order, investigators can secretly place a GPS tracking device on a suspect’s car to follow their every move

Law enforcement agencies are also using text messages, cell phone records and credit card transactions to find out where a suspect was and what they were doing at the time of the crime.

“There is a child killer on the loose and that's why we're going to catch this person and bring them to justice,” Breseler said.

Investigators were reluctant to release more specific information on how they solve crimes, so they don’t tip off suspects. Sources say a lot of crimes are solved through old-fashioned police work and they often pay confidential informants for information The FBI has studied numerous offenders and their behaviors and investigators can use that information to develop a profile of a potential suspect.

Now that the killer knows he's not completely in the clear and evidence he left behind could lead to him, experts say he will probably start paying close attention to the new and might start to panic, drink more than usual or act strangely enough to draw attention to himself and that could also help get him caught.