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.
It was later discovered that the sender was based out of Nigeria. 
( z1 discover :ARG1 ( z2 base :ARG1 ( z3 person :ARG0-of ( z4 send ) ) :location ( z5 country :name ( z6 name :op "Nigeria" ) ) ) :time ( z7 after ) )