FEC 807 (ES44C4) , LNG Fuel Tender, GE Evolution NextFuel locomotive #3000.
From Wikipedia: In 2013, General Electric built one ES44AC, GECX 3000, as a test bed for their NextFuel natural gas power kit. The engine runs on liquefied natural gas from a fuel tender. The unit is currently part of BNSF's GE LNG test set, partnered with BNSF ES44AC no. 5815.
Some stills. Sorry for the quality, moving pretty fast and hard to find a decent spot to take pictures.
FEC 807 was lead locomotive
Followed by the Liquified Natural Gas tender
Then the GE NextFuel locomotive.