What's The Difference?
While the on scene roles of first and last responders differ, their objective is the same: to find answers.
First responders, the police, are concerned with whether or not a crime has occurred while last responders, the coroner or death investigator, work to determine the cause and manner of death. The last responders will benefit from the experience, expertise and resources provided by first responders. First responders will benefit from the last responder's experience and expertise in establishing the cause and manner of death.

first re-spon-der
noun
noun: first responder; plural noun: first responders
someone with specialized training who is among the first to arrive and provide assistance at the scene of an emergency, such as an accident, natural disaster, or terrorist attack.
First Responder

last re-spon-der
noun
noun: last responder; plural noun: last responders
someone with specialized training who is among the last to arrive on the scene of any violent, suspicious, unattended, unexpected, or unexplained death.