To the extent that sequencing is related to the fact that we will have enough vaccine for the whole population within a matter of weeks, unlike other jurisdictions where it will be many months, or not at all for some...it's about timing as it relates to that.
The reason certain groups are there is because they are most vulnerable to get severe disease. You want to protect them first because they're the ones more likely to die. In general, firefighters and police are not more likely to die from this disease. You also want to ensure that those who are actually going to manage the pandemic and those who are going to care for those who are ill, if they do get ill, are immunized first so that they're available to actually work in the hospitals to care for people.
In general, first responders will be very quickly immunized, and certainly if they have underlying risk conditions, then they're obviously at the top as well. But that is the target for the first group versus the second group, which includes all first responders as well as others.