More info from the Truckee PD's Facebook page is here:
https://www.facebook.com/truckeepolice/posts/796320660566227
It's worth reading, but the key facts according to the post are that Salazar was found by the tracks at "
the far east end of Truckee" (i.e. before it arrived at the station) and "the incident originated and appeared to be entirely contained on the Amtrak train". According to the post, "Aaron never disembarked in Truckee, as he never made it to the Truckee station, and there is no information to suggest Aaron had any connection to Truckee or interactions with anyone from Truckee".
The investigation was turned over to Amtrak "after our preliminary response" and the Truckee PD is "not actively involved in the investigation". The post opens by saying:
"It is the policy and best practice of most public safety organizations to not comment on another agency’s investigation, particularly if that investigation is active. However, since much of the information that is circulating on social media and in some news stories is inaccurate, speculative, or simply false, the Truckee Police Department would like to clarify a few things".
It closes with:
"The Truckee Police Department has no control over the release of substantive information in this incident, since another agency is handling the investigation. We do ask, out of respect for Aaron, his family, and for the investigative process that speculation, guessing, or rumors not be the basis for drawing conclusions", and refers further questions to Amtrak's police.
The timing is interesting. The post reiterates what the log stated, that the Truckee PD responded at about 11:30am, but then says "it was almost immediately discovered that Aaron was a ticketed passenger on the west bound Amtrak train that had passed through Truckee earlier that morning". 5(13) left Colfax on time at 11:48, and then was approx. 40 minutes early (give or take) the rest of the way to Emeryville.
It doesn't seem as if Amtrak PD treated it as a crime scene.