I did some Googling for your question...and it does appear this is becoming another "fad" of terrorism...
France had an outbreak of clown terrorism in 2014; police put some of the blame on social media. Also, at least one of the clown episodes in France seemed to copy the American movie, THE TEXAS CHAINSAW MASSACRE.
I followed one of the YouTube links to a trilogy of clown "pranks;" all very threatening...along with a link for you to purchase your own clown costume. One of the videos got 74 million hits in 18 months, another 46 million hits... training films in terror.