I’d put money on it bring individuals as opposed to terriost group.
ISIS has been calling for “lone wolf” attacks using vehicles and knives for some time. The Nice attack was just such an attack. That one form of an ISIS attack. US State Department has been warning tourists to avoid places like Christmas markets. I am quite surprised after Nice there where not concrete blocks in place, either that or the lorry has pushed through them.
I hope the Polish truck driver is ok, he has not been heard of since 4pm. Theory is the truck was hijacked. A person was found dead in the passenger seat of the truck.
The Zurich shooting was near an Islamic Centre as opposed to inside. Not clear who where the casualties.