Do you have a source saying he was a convert?
http://abcnews.go.com/US/san-bernardino-attack-fbi-questions-alleged-assault-style/story?id=35626957
“An individual associated with a local mosque, who asked not to be named, said Marquez started coming there three or four years ago, after he had converted to Islam. The person said Marquez was shy and polite, but did not seem that bright. Two members of Farook’s family, but not Syed Farook, attended the same mosque, the person said.”
Turns out he is married to the sister of the dead jihad woman. He converted to muzzie yet has Mexican name.