The plane crash that killed Yevgeny Prigozhin was caused by a “small explosive device slipped under the wing” of the Wagner boss’s jet in an assassination plot organized by Vladimir Putin’s closest ally, according to a Wall Street Journal investigation. The newspaper, citing sources in both Western intelligence and a former Russian intelligence officer, says the Aug. 23 killing was “put in motion” by Nikolai Patrushev—the veteran spy chief who had long advised Putin to rein in the mercenary chief. With Putin’s blessing, Prigozhin had built up a private army running a multibillion-dollar empire in Africa and other parts of the world. But as Wagner’s forces took over in the key Ukraine battlefield of Bakhmut, he became too powerful for the Kremlin to control and after a mutiny in June, the decision was taken to kill him, the Journal reported. In the words of a former CIA station chief, Putin allowed Prigozhin to carry on after the abortive coup, but only as a “dead man walking” while his collaborators were rooted out. After that, Patrushev’s plot was put into action, with Prigozhin and his aides eliminated on a flight from Moscow to St. Petersburg.