Syed Rizwan Farook and Enrique Marquez met as teenagers in a corner of America that could have been anywhere — clipped lawns, modest ranch-style homes, driveways stacked with cars.

But in a matter of years, they were plotting against their own Southern California community, envisioning themselves slaughtering college students and freeway motorists with pipe bombs and bullets.

FBI documents provide a window into their relationship, and how a turn to radical Islamic ideology ended with Farook and his wife dead and Marquez facing federal terrorism-related charges.

HOW DID THEY MEET?

By happenstance, it appears. In 2005, according to an FBI affidavit, Marquez moved next door to Farook's family on Tomlinson Avenue in Riverside, California, about 55 miles east of downtown Los Angeles.

The two teens — Marquez was four years younger — met in Farook's garage.

Farook, a Muslim, began educating his new friend about his religion, and by late 2005 Marquez was praying frequently at Farook's home and had visited a mosque.

By 2007, Marquez converted and became a Muslim.

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WHEN DID RADICAL IDEOLOGY SEEP INTO THE RELATIONSHIP?

According to the FBI, their discussions shifted shortly after Marquez converted.

The two began discussing the extremist views of radical cleric Anwar al-Awlaki, an American-born al-Qaida ideologue killed in a U.S. drone strike in Yemen in 2011.

Marquez began looking into the ideas of Imran Hosein, a religious scholar who promoted living under strict Islamic law.

By late 2011, Marquez was spending most of his time at Farook's home, where he read Inspire magazine, an official publication of al-Qaida in the Arabian Peninsula; watched videos produced by al-Qaida's affiliate in Somalia; and studied radical material online.

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WHEN DID THEY BEGIN DISCUSSING POSSIBLE ACTS OF TERRORISM?

In 2011, Farook and Marquez began planning attacks "designed to maximize the number of casualties" on a local college they had attended and an often-clogged freeway, state Route 91.

The plans called for building pipe bombs to use in the attacks. They envisioned halting traffic on the freeway with explosives then firing at trapped motorists, or tossing pipe bombs into a crowded cafeteria at Riverside City College. They chose the college because they were familiar with the campus.

Marquez was picked to buy weapons because they feared Farook's Middle Eastern appearance — his parents were born in Pakistan — might arouse suspicion. Marquez bought two AR-15 rifles from sporting goods stores in 2011 and 2012.

In 2012, they made multiple trips to gun ranges for practice. Marquez also bought powder for explosives.

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WHY DIDN'T THEY EXECUTE THOSE ATTACKS?

According to the FBI affidavit, Marquez told investigators he distanced himself from Farook and stopped plotting with him in 2012 for a variety of reasons, including the arrest of several men in Southern California that year on terrorism-related charges for allegedly plotting to kill Americans overseas.

Farook, 28, and his wife, Tashfeen Malik, 29, died Dec. 2 in a gunfight with police after killing 14 of his co-workers at a holiday gathering.

Marquez, 24, was charged Thursday with terrorism-related counts, including illegally buying two assault rifles used in the attack. Prosecutors said there is no evidence Marquez participated in the San Bernardino massacre or had advance knowledge of it.

In a Nov. 5 Facebook post, Marquez wrote: "I lead multiple lives and I'm wondering when it's all going to collapse."