Vivek Shah, 25, is facing federal charges that he threatened to kidnap and kill Weinstein's family if the producer of "Shakespeare in Love" didn't wire $4 million to an offshore account.
Shah describes himself online as an entrepreneur. According to court documents, Shah sent menacing letters not only to Weinstein, but to four other millionaire tycoons.
"Each of these letters contained a threat to kill named members of the recipient's family unless a large sum of money was wired to an offshore bank account," Postal Inspector Joshua Mehall said in a sworn affidavit.
Weinstein's office is making no comment on the plot. The three other alleged victims include the owner of an NHL team, an oil company executive and a coal mining tycoon.
Investigators say Shah demanded a total of $13 million and that there were signs he planned to use deadly force to carry out his threats. He had contacted a gun range in Los Angeles so he could learn to shoot.
Shah allegedly developed a detailed scheme to hide his identity while carrying out the shakedown, buying prepaid debit cards to wire extortion letters, using false IDs and setting up offshore accounts.
"Mr. Shah strikes me as someone that's frustrated that he can't get into the mainstream of Hollywood," said ABC News consultant Brad Garrett.
Two weeks ago, federal agents raided a modest West Hollywood apartment that he shared with two roommates. It was days before that when deputies received a call from one of his roommates.
"He had an altercation with a girl that was living there, and they got in a big fight," said neighbor Casey Schteamer. "She ended up calling the police and getting a restraining order against him."
Investigators say while questioning Shah, they found he had a fake driver's license - a name that coincided with other transmissions used in the alleged plot.
Shah was arrested Aug. 10 by federal agents at his parents' home near Chicago. He is now in federal custody in West Virginia where the coal mining executive lives.
ABC News contributed to this report.