If the attack had been carried out by a known terrorist organization, we would already have heard about it. So it appears this wasn't an al-Qaeda or Kurdistan Workers' Party (PKK) operation. Or maybe it was, and for some reason that we are unaware of they have preferred not to claim responsibility for it.
It is obvious that a terrorist attack against one of the main crossing points for Syrian refugees into Turkey has something to do with Turkish-Syrian relations. It was about exposing and perhaps interrupting Turkey's support for the Syrian opposition. Therefore, perhaps the Assad regime is behind this bloody blast. However, given the complexity of the situation, one has to be more suspicious than that and dig for other possible explanations.
The immediate result of the attack was the tightening of security measures along the Turkish-Syrian border, which has complicated the lives of many. Turkey was already prepared to enhance security there, because we know that the border traffic to and from Syria is not only about humanitarian assistance. Ankara's worries about some of the people who cross through the checkpoints without much control grow stronger with each passing day. The permeability of the border is, in fact, a serious security threat for Turkey. The Turkish government had to take some action anyway, but it would be preferable not to be compelled like this.
The Syrian-registered minibus blew up on the Turkish side, which means somebody allowed it to cross the border, hinting at complicity between some Turkish and Syrian elements. So maybe the right question is: Who would like Turkey to downgrade its relations with the Syrian rebels?
All the answers we could formulate will be highly speculative right now, but it is hard to suggest that there could be only one terrorist organization behind all this. It seems more like there are foreign governments behind this operation. Nevertheless, if this attack was perpetrated by players at the service of Iran or some European countries that want to keep Turkey away from the Syrian crisis, Ankara will not accept this and on the contrary, it will become more involved.
It is true that the controversy about the composition of the Syrian opposition is growing. It is frequently said that radical Islamist elements are growing stronger, and maybe the purpose of this attack was to warn everyone who supports these groups. If this theory is correct, looking for Middle Eastern perpetrators will be meaningless, and one will have to look far beyond.
What comes next will be decided mostly by Turkey's attitude from now on. Turkey may choose to accept or refuse this attack's message. If Ankara tightens security measures along the border and makes sure the help it provides for the Syrian refugees doesn't fall into the wrong hands, this kind of attack will stop. If not, this week's attack will only be a beginning. It is noteworthy that the attack was perpetrated on the Turkish side of the border and killed civilians. This is a serious warning. The next attack, if it happens, may have the intention of killing more Turkish citizens, provoking the ordinary people to criticize the government's Syria policy and putting the governing party in a delicate position.
When the background of this terror attack becomes clear, Turkey will certainly adopt some measures, even though these will probably not be made public. The problem is, if the intelligence services of foreign governments are indeed behind this attack, even if we identify the one who pulled the trigger, we will never be able to expose the real plotter. Exactly like the assassination of three Kurdish women activists in Paris.