So, I wonder what this is about:

Amtrak passengers will be subjected to random screening of their carry-on bags as part of a new security initiative that will include armed officers and bomb-sniffing dogs patrolling platforms and trains, an Amtrak spokeswoman said Monday.
Details of the new effort, which were first reported by The Associated Press, will be announced Tuesday, the spokeswoman, Tracey Connell, said.

Unlike airlines, Amtrak has had few visible changes to security since the September 11, 2001, terrorist attacks, but in recent years trains have been the targets of terrorism.
[…]
Amtrak chief executive Alex Kummant told AP the new measures are not a response to a “new or different specific threat,” but rather, he said, “just the correct step to take.”

Yeah, I’m not buying it. Of course the government official doesn’t want to cause panic or create a drop in the commuter traffic so they won’t tell us if there’s a threat.