My guess is a couple of rounds of small arms fire into the boat before it departed :-)
Pirates released after assault operation near Gulf of Aden apparently perished ) AFP/Pierre Verdy 12:1611/05/2010
The Somali pirates who were captured in an assault operation after hijacking a Russian tanker near the Gulf of Aden and then released by Russian military officials have not reached the coast and have apparently perished, a top-ranking source in Russia's Defense Ministry told journalists on Tuesday.
Russia's Moscow University tanker was hijacked last week near the Gulf of Aden. Ten pirates were captured and one was killed in the assault operation.
The captured pirates were initially to be sent to Moscow for prosecution, but Russian military officials then made the decision to release them, citing the absence of a legal base to carry out prosecution procedures against pirates.
The pirate's boat reportedly disappeared from radars an hour after they had been released by the Russian military.
//Alif J.A. Terranson, CISM PO Box 771026 Saint Louis, MO 63177 (618) 558-5854 -- "Never belong to any party, always oppose privileged classes and public plunderers, never lack sympathy with the poor, always remain devoted to the public welfare, never be satisfied with merely printing news, always be drastically independent, never be afraid to attack wrong, whether by predatory plutocracy or predatory poverty." Joseph Pulitzer, 1907 Speech