A video did it.... Just ask Hillary. Actually all jest aside they are more concerned with proving ISIS doesn’t have Stinger like missiles.
********************************************************************************
Well, the warhead of a Stinger is relatively small (only several kilos) but VERY powerful. It could be easily and quickly jury-rigged together with a relatively primitive barometric detonation device and do the job very effectively.
As someone up thread has pointed out, whatever the bomb was made of will have left signatures that would allow SPECIFIC identification by knowledgeable technical experts.
In other words, it would be turned into a bomb. Why not just use some Semtech and a timer. That would be well withing the terrorists technical levels.