ISIS has everything to do with islam, they are following the teachings of the prophet to the latter. If in doubt ask @Guru247 and you will get your answer

True, we can't shy away from the fact that ISIS has come out and taken claim of this attack. Yes, they have said Islamist extremists have done this act.

But @anti_burglar and @Matoe, get this correctly:

INCORRECT!!! INCORRECT!!!

You can't attach yourself to a religion when you don't follow the laws of that religion. These so called Islamist extremists loose the right to be part of Islam the moment they go against the "book they claim to follow". The moment they promoted terror, violence, murder etc they lost the right to be part of any religion.

THEY ARE JUST TERRORISTS!! NOTHING MORE, NOTHING LESS, THEY ARE JUST TERRORISTS!

Millions and millions of Muslims right now are embarrassed and ashamed of this. They are following and practicing their religion in the right ways and we don't apologize for following our religion. Because these millions and million Muslims right now are horrified and disgusted at these attacks!

Even Hitler did murder in the name of religion but we cannot blame those who call themselves for his action

The difference, you ask? Well, it is happening now, in our lifetime, in the age of enlightenment, development, science and knowledge. Oh, and criticism.

It doesn't matter,it's a learning curve

1. First it was the pagans who were killing the Christians and banning of Christianity , churches and temples in the years 300-400.
2.Then the Christians came, they were ,persecuting forcing conversion and killings by beheading of Jews and Muslims in the years 380-1900(I'm sure some Muslims, jews and African with their Gods were wondering why is this happening now in our lifetime of development and knowledge)

So now its turn of the radicalized islams who are doing what some radicalized pagans and christians did(and of course you are here wondering why is this happening in this lifetime of exposure,development etc)

Next it will be Hamburglar who will beheading your Christians,Muslim, Jews etc, from his post you can read some form of radicalization.

Be still and know that He is God!
2.

here is the big question.... what determines what 'text/scripture' to follow or what not to follow? here are two examples that come to mind as I pounder this...
1) In the story of Lot...Two men who were really angels appeared in Sodom where Lot lived with his family. The wicked men of the city surrounded Lot’s house seeking to have homosexual relations with the angels. Lot begged the men of the city not to do this evil thing, and he offered up his two virgin daughters to them instead. God rescued Lot coz he was "a righteous man, who was distressed by the depraved conduct of the lawless" - OK?
2) The story of the Benjaminite who gave his daughter and concubine out to be gang raped and later cut his concubine, limb by limb, into twelve parts and sent them into all the areas of Israel. Right?

My question - what enables you to dismiss this text and not kill your "concubine" or "give your daughers out for gang raping" or other myriad of really disturbing or ridiculous texts? What makes you not follow these ones to the letter? if you have that 'thing' that makes you not 'give your daughters out to gangs of robbers'... why not allow by pass the text for direction and use that 'thing'? Because some of the things in there are horrible and going forward we will have nut cases that literally believe these things and will consider themselves 'true' believers and with the ease of getting weapons - they may end up being your neighbour!