I was under the impression that it is widely believed that the Soviets were behind it.
The hit was orchestrated by the KGB using their surrogates in the Darzhavna Sigurnost, the Bulgarian Secret Service.
Agca was a member of the Turkish Grey Wolves, the military wing of the neo-fascist, Turkish MHP - the National Action Party. Agca and his co-gunmen were trained in Sofia and had long been groomed by the DS for deniable "wet work".