[khed]

There are a couple reasons why he might do this that I can think of.

1). He didn't know how many people were going to come in or how serious they would be. Triage in MCI does depend to a certain degree on what your facility is capable of and the expected volume and status of patients. If he underestimated the volume or criticality of the patients about to come in he might have put more into the red pod than he would have otherwise. Underestimating seems plausible in this case because this was the worst mass shooting in history in the US.

2). Medicolegally he might have a fear that he would be judged harshly if he didn't automatically try to save everyone.