The Paris Terrorist Killers: Why did that one guy Bring his Passport to the Suicide Attack?

Ever since I heard the news that they found a passport next to one of the suicide attackers in Paris I wondered why he brought the thing with him.

- Ahmad al-Mohammad? -

Close to the body of a second bomber outside the Stade de France, investigators found a Syrian passport in the name of Ahmad al-Mohammad, 25, who was born on September 10, 1990, in the Syrian city of Idlib.

A passport bearing that name had been registered on the Greek island of Leros on October 3, with the attacker's fingerprints matching those taken during the registration process. The holder of the passport was later registered as crossing from Macedonia into Serbia where he formally applied for asylum, Serbian officials said.

But investigators are still trying to verify if the passport is indeed genuine and the name is not known to French anti-terror police. Serbia detained a migrant on Monday whose passport contained the same data.

It seems to me to be a forged passport to change the persons identity. That would make sense if ISIS wanted to make it seem that the Syrian refugees harbor all sorts of terrorist killers in their midst. Europe will reject them coming in and ISIS would then be able to recruit/extract revenge/kidnap them. 

I just couldn't understand why he would bring that passport with him. Perhaps he just got to Paris and the attack was just days away so he couldn't stow it somewhere. However, I think it was just a forged passport that got him in from where ever so he could take part. That where ever might be very important to the investigation. Also I wonder how many additional people are traveling under that name?