Denver’s airport train is fully operational again following a fatal collision with a van at a railroad crossing.

Passengers had to take a bus part of the way Tuesday following the crash but full service from downtown to the airport resumed Wednesday.

Police are focusing on whether the driver of the van intentionally pulled in front of an airport-bound train in Aurora.

The man drove past a police officer guarding the railroad crossing and drove onto the first of two sets of tracks before the crossing gates and lights activated. Police say surveillance video showed the van stayed there for 38 seconds before driving onto the second set of tracks as the airport train was approaching.

The driver was killed. Four train passengers suffered minor injuries.