An FBI dive team conducts a search for any evidence, that may have been left by the husband and wife behind the San Bernardino massacre,  at Seccombe Lake Park, in San Bernardino, California, on December 10, 2015. David Bowdich, assistant director of the FBI's office in Los Angeles, told reporters there were indications that US-born Syed Farook and his Pakistani wife Tashfeen Malik had visited the park where Seccombe Lake is located on the day of the December 2 attack or previously.  AFP PHOTO/ RINGO CHIURINGO CHIU/AFP/Getty Images
RINGO CHIU/AFP/AFP/Getty Images
An FBI dive team conducts a search for any evidence, that may have been left by the husband and wife behind the San Bernardino massacre, at Seccombe Lake Park, in San Bernardino, California, on December 10, 2015. David Bowdich, assistant director of the FBI's office in Los Angeles, told reporters there were indications that US-born Syed Farook and his Pakistani wife Tashfeen Malik had visited the park where Seccombe Lake is located on the day of the December 2 attack or previously. AFP PHOTO/ RINGO CHIURINGO CHIU/AFP/Getty Images
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Story highlights

Friend of killer says he had worked on pipe bombs before with Syed Rizwan Farook

For the second straight day, divers search lake near where the shooters killed 14

(CNN) —  

More than one week later, authorities are still digging to make sense of the San Bernardino massacre, piecing together the clues they’ve compiled so far and trying to discover more, including by investigating the shooters’ electronic trail and searching a lake near where the carnage occurred.

The identity of the killers, Syed Rizwan Farook and Tashfeen Malik, is not in doubt. But investigators want to find out more about who this married couple interacted with, how they hatched and carried out the plot, and why.

These are the latest and most significant investigative leads so far:

Friday

Friend of killer says he helped build prior pipe bombs

Enrique Marquez, a former neighbor of Farook, told investigators he and his friend previously built pipe bombs, law enforcement officials said.

Marquez said he had nothing to do with devices found at the home of Farook and Malik, or the ones that apparently failed to go off at the site of the shooting, the officials said.

Marquez, who has spent several days being voluntarily interviewed by the FBI, portrayed the two men as hobbyists experimenting with building the devices, the officials told CNN.

He also boasted, one official said, that if he had made the bombs they would have gone off.

Marquez has emerged as a person of interest in the San Bernardino shootings because he bought rifles used in the attack. He has not been charged with a crime.

Divers search a small lake near where shooters had been, the FBI says

Divers ended Friday evening a second search of a small lake in a park a few miles from San Bernardino’s Inland Regional Center, where 14 people were killed last week.

David Bowdich, the assistant director in charge of the FBI’s Los Angeles office, wouldn’t comment on what they were looking for. But he said Farook and Malik were in the area “at some point,” without specifying if this was before or after the massacre.

One of the items divers likely are looking for is a missing hard drive from the couple’s computer.

Bowdich has said the search will take several days.

Thursday

Farook was in the same ‘social circle’ as convicted terrorist, FBI believes

The FBI believes Farook had ties to a group of jihadists in California who were arrested in 2012 for attempting to travel to Afghanistan to join al Qaeda.

Specifically, investigators are taking a new look at one of the four men who was arrested in the 2012 case, Sohiel Kabir. Kabir, who was convicted and sentenced to 25 years in prison, was the recruiter who helped radicalize others.

The 2012 probe happened in Riverside, California, not far from San Bernardino. Farook was in the social circle of Kabir, officials told CNN.

The FBI initially investigated five men as part of the Riverside group. The fifth wasn’t arrested and hasn’t been identified. But Farook was not among those investigated at the time, the officials said.

Wednesday

Marquez says Farook considered terror plot in 2012

Marquez told investigators that he and Farook conceived a terror plot in 2012, but abandoned their plans after the FBI arrested an unrelated group in Riverside that had been planning to join al Qaeda in Afghanistan.

Marquez checked himself in to a mental health facility after the San Bernardino attack.

He is cooperating with the FBI, but investigators are still trying to corroborate the information he has provided, including details of the alleged 2012 plot.

Marquez claims he knew nothing about the San Bernardino shootings. He has not been charged with a crime.

That same friend’s marriage – t