Starting in 2007, Ûsoyan was embroiled in a gang war with Georgian mobster Tariel Oniani, who was seeking to reestablish himself in Moscow. Several of Ûsoyan's top lieutenants were killed including the Armenian national Alek Minalyan, a man allegedly in charge of extorting construction firms working on the 2014 Winter Olympics. In July 2008 police raided Oniani's yacht as a meeting took place amongst the criminal leaders in an attempt to settle the conflict. Ûsoyan was not however amongst those detained. He later gave an interview to a newspaper, denying the stories of escalating violence and stated that "We are a peaceful people and don't bother anybody, we are for peace in order to prevent lawlessness". Vyacheslav Ivankov was brought in to mediate the conflict, in which he sided with Ûsoyan's faction. He was however shot by a sniper while leaving a Moscow restaurant in July 2009, and died of his wounds in October that year. Although he did not attend, Ûsoyan sent an elaborate wreath to Ivankov's funeral saying "To our brother from Grandpa Hassan". In April 2010, Ûsoyan was arrested by Ukrainian security forces after entering the country illegally using false documents. His business in Ukraine was allegedly connected to a rift with an Armenian organized crime group. On 16 September 2010, Ûsoyan was shot by a 9mm calibre bullet fired by an unidentified assailant in central Moscow, but survived the attack along with his bodyguard who was also wounded. It was at first announced to the press that Ûsoyan had died to ensure his safety. In the early 2010s the Obama administration placed sanctions on members of the alleged criminal organisation the Brothers’ Circle. It has been speculated that the so-called Circle is a stand-in for Ûsoyan's network.
On 16 January 2013 and a month before his 76th birthday, Ûsoyan was shot in the head by a sniper perched on the sixth floor of an adjacent apartment building after leaving a restaurant which served as his 'office', and despite efforts of his bodyguards and ambulance workers he died en route to the hospital. The family decided to fly Ûsoyan's body to be buried in his native Tbilisi, but the Tbilisi International Airport refused to accept the plane. His death was thought to be likely to spur chaos in the criminal world. The day Ûsoyan was shot dead, an Armenian crime fiction writer, Sergey Galoyan said, in a conversation with a local news website, that the mafia king's murder might be linked to a certain unrest in the criminal world, particularly the construction of the Sochi Olympic facilities which are said to have attracted considerable investments. The main suspects behind Ûsoyan's murder are Tariel Oniani and Rovshan Janiev.
