Some of the emails had the subject line, "Think Twice." They were sent from a spoofed email address. The sender claimed to have had an associate plant a small bomb in the recipient's building and said the only way to stop him from setting it off was by making an online payment of $20,000 in bitcoin.
Bitcoin is a form of payment
( z1 form :manner-of ( z2 pay ) :domain ( z3 currency :name ( z4 name :op "Bitcoin" ) ) )