(CNN) -- It took mere hours to confirm that the person killed in a compound near Pakistan's capital was Osama bin Laden.
How did officials know that the man who was shot in the head Sunday was really the world's most wanted terrorist?
DNA, among other things, senior officials told CNN.
Officials compared the DNA of the person killed at the Abbottabad compound with the bin Laden "family DNA" to determine that the 9/11 mastermind had in fact been killed, a senior administration official said.
It was not clear how many different family members' samples were compared or whose DNA was used.
During a press briefing Monday afternoon, John Brennan, President Barack Obama's adviser on homeland security and counterterrorism said they had "preliminary DNA intelligence" ahead of the strike.
Among the five killed in the compound, one of them was one of bin Laden's adult sons, officials said.
Also to identify bin Laden, a visual ID was made. There were photo comparisons and other facial recognition used to identify him, the official said. A second official said that in addition to DNA, there was full biometric analysis of facial and body features.
Dr. Victor Weedn, a forensic pathologist who helped pioneer the military's DNA identification program,said it's likely that the military would have samples for high-profile terrorists like bin Laden.
"The U.S. government would have an interest in looking for samples of DNA wherever they might find it, whether from family members or places he might have been, and store those samples," he said.
Essentially, scientists take DNA from the person's body, and compare it to another source like a sample collected from the individual at a previous time, or the DNA of a close family member.
DNA samples can be obtained from a multitude of sources, including discarded chewing gum, a toothbrush, a half eaten sandwich and even an envelope the person may have licked to seal, for example.
To confirm bin Laden's identity, officials probably used several methods, said Michael D. Kirkpatrick, a retired senior FBI assistant director who had worked in creating a biometric database of terrorist identities. He was not involved in the bin Laden case and spoke generally about the identification process.
"I'm sure in this particular instance, given the magnitude of the individual involved and the likelihood of international scrutiny and doubt on the part of some people around the world, that they would err to the extreme -- to over-identify him," he said.
"This is something you really can't make a mistake. You have the president announcing to the world it happened. Effectively, they would look at all these [biometrics] and make a decision. "
DNA is the most reliable measure, experts said.
This can be collected through a cheek swab, blood, hair, fingernail, or even saliva from a cigarette.
According to the U.S. Human Genome Project -- which helped to identify the more than 20,000 genes in human DNA -- forensic experts use DNA to distinguish a person's genetic footprint, by looking for matches from a sequence of small, repeating markers at different locations on the person's genome.
Each of us has a unique genetic fingerprint, even though only one-tenth of 1 percent of the 3 million DNA bases differs from one person to the next.
Using family DNA to compare with a person "would be pretty darn accurate," said Kirkpatrick.
This would work much like a paternity test proving genetic relations, said Max Houck, a former FBI supervisory physical scientist.
Computer software and human DNA analysts could read the data to make the confirmation.
The FBI's forensic system relies on 13 DNA regions that vary for each individual and use that data to create a genetic profile of that individual. It's unclear if this is the method intelligence officials used to identify bin Laden's body.
Facial recognition software programs compare photographs of the person.
Such programs take the topology of the face and essentially read the features, where the person's eyes, nose, lips are located, their proportions and measurements. The facial recognition programs map the geometry of a person's face and can compare images.
They identify points of reference on the face and read whether it's the same person, said biometrics experts.
Facial recognition can also work compare facial features, the shape of the skeletal structure, moles, scars and other skin marks.
A visual ID
Bin Laden would've stood out to the trained U.S. military team who entered his compound.
"He's a distinctive person, for that part of the world," Kirkpatrick said. "He's 6-feet, 4-inches. He's gaunt. There are plenty of photographs of him."
Matching features like bin Laden's height would've helped.
A full biometric analysis could mean wide variety of things including fingerprints, palm prints, DNA analysis, iris scans, said Houck.
It's unclear exactly what type of identification tools officials used in this category to determine bin Laden.
Some methods also use hand geometry, looking at photos to see the width of palms, the physical features of their hands or even the vein patterns to confirm a person's identity, said Houck, who examined remains after the 1993 fire in the Davidian compound in Waco, Texas, and also worked to identify 9/11 victims during his career with the FBI.
CNN's John Bonifield and CNN Wires contributed to this report.