was he operating under a legal/official authority to confront and/or pursue suspects? If not, he shouldn’t have pursued, confronted, and killed.
Have you ever heard of a citizens arrest?
Ordinary citizens have the power and authority to pursue and apprehend criminal suspects. Inherently with this power comes the authority to conduct an investigation, to the extent such investigation itself does not break statute.
By your rationale, a homeowner who hears breaking glass in his driveway has no authority to go outside and see what the hell is going on.