A California man was arrested on Thursday on suspicions he supplied guns to the married couple who killed 14 people in a shooting rampage in San Bernardino, California, on December 2. Enrique Marquez, 24, was once the neighbor of gunman Syed Farook, and has been charged with conspiring to provide material support to terrorists.

Court documents show that Marquez had also planned other mass atrocities with Farook, such as an attack on a local college and a major highway, but neither was ever carried out. Marquez purchased two AR-15 assault rifles after the pair worried Farook's Middle Eastern appearance would make gun sellers suspicious. He also purchased material to make pipe bombs, which were originally planned for the college attack that never materialized.

Marquez was also charged with immigration fraud, as authorities alleged he had entered into a "sham marriage" to the sister of Farook's brother's wife.

"Mr Marquez conspired with Mr Farook to commit vicious attacks," said US State Attorney Eileen Decker.

"Even though these plans were not carried out, Mr Marquez's criminal conduct deeply affected San Bernardino County, Southern California and the entire United States when the guns purchased by Marquez were used to kill 14 innocent people and wound many others."

Decker added that there was as of yet no evidence that Marquez knew of the December 2 attacks in which Farook and his wife Tashfeen Malik massacred 14 people at a holiday party in an "Islamic State"(IS)-inspired attack.

The FBI said Marquez and Farook were engaged in martyrdom discussions online, and both became supporters of IS through the Internet.

es/jm (AP, dpa, Reuters)