Usually, it seems, when the story says that they don’t know the motive, it means that they know the motive and don’t want to say.

Israeli police say a 19-year-old man with American and Israeli citizenship is suspected of making threats against Jewish institutions worldwide.

Police arrested the suspect in the south of Israel on Thursday morning over threats against Jewish communities in the US, New Zealand and Australia.

[…]

But Israeli police spokesman Micky Rosenfeld said on Thursday the latest suspect’s motives are unclear.