From the NY Times Al Qaeda/ISIS correspondent Rukmini Callimachi (@rcallimachi):
1. Important update on Dortmund bus attack by @bopanc. Explosive used was military-grade (uncharacteristic of ISIS)
2. In nearly every successful & foiled IS bomb plot in Europe, explosive used was TATP. It's become their signature
3. The reason is because TATP is made from commonly available household ingredients. You can buy them over the counter, avoiding detection
4. As @bopanc writes, explosives used have been employed in past by Nazi groups. It was framed to look like IS but there were a # of errors
5. For example letter left at scene claiming attack on behalf of ISIS, referred to "unbelievers" in German. ISIS acolytes refer to "kuffar."
6. And as @charliewinter noted, letter fails to pledge allegiance to IS leader Abu Bakr al-Baghdadi, which has become de rigueur.
7. After every inspired attack, ppl flood my timeline saying, "He just learned that on the internet." Sure, that's how they do it.
8. But as fake ISIS letter left at scene of Dortmund bus attack shows, it's not as easy as you might think to absorb the ISIS lingo.
9. If sources quoted by @bopanc's are right & this was an attempt to frame IS, you'd expect they spent some effort trying to ape IS terms
10. Despite that effort, they still made enough mistakes that anyone watching ISIS closely like @PeterRNeumann realized something was off
11. A final clue: ISIS never claimed it. I realize many continue to believe ISIS "claims everything." The fact is they don't.
12. The investigation remains open and ISIS may still surprise us. But from what is now known, this attack would be *atypical* of ISIS.
