When Osman B. arrived in the airport of Antalya he was immediately arrested by the Turkish police. He was suspected of “terrorist propaganda”. Osman B. was born 1983 in Turkey and became a german citizien in 2011 and lost his Turkish citizenship in 2012. He was travelling in the end of July to Antalya with his family for a vacation when he was arrested.

Osman B. was allegedly sharing “terrorist propaganda” on facebook. It’s not clear what he exactly did. The current lead is that he either shared “PKK-positive” content or just liked “PKK-positive” posts and is now being held accountable for the content.

The Turkish state launched a new offensive against “terrorism”. The Turkish Interior Minister said in his campaign “In Germany, in Europe, there are those who attend terrorist organization events then go on vacation in Antalya, Bodrum and Mugla […] Now we've taken action against them. “, continuing “All right then, let them come and go to prison directly from the airport. Being in prison isn't so easy. From now on it won't be easy to commit treason abroad then come to Turkey for fun and good times”.

Osman B. instantly was taken into custody because of “risk of flight” and is now facing several years of jail if convicted. Apparently in this rotting, oppressing, exploiting system facebook likes are enough to be considered a terrorist, if they show you have an opposition against it.
A clarification about the PKK is documented here.