[Gondring]

He tried to buy Ammonium Nitrate as well. Do you think that choice suggests something too? I don't know anything about explosives.

Yes, it suggests to me that he was acting alone, trying to find something that would work, and was able to find a recipe with obtainable ingredients by reading jihadist publications.

[popdonnelly]

"Yes, it suggests to me that he was acting alone,"

It could also suggest that he was hanging out with jihadis who thought it would be a cool idea if he made a car bomb.