Social networking sites like Twitter were abuzz after media and public relations executives said in their posts that they had coffins delivered to them by unnamed senders on Monday morning.
Some speculated that it was a form of intimidation against the media for their reporting, with a politician condemning the act as a threat to free speech.
Seeing growing dread, marketing expert Sumardy Ma admitted that he was responsible for the deliveries.
"We're launching a book titled Rest in Peace Advertising Killed by Word of Mouth," he told the Detik.com news website.
"We apologise if this has caused restlessness among members of the public," he said, adding that he had planned to send 100 caskets to media companies and people.
Police were not amused. They arrested Ma and put a police line in front of his office.
It was not clear what charges, if any, Ma was facing.