The officer had tried to stop Fuiavailili Fa'au Gago from filming the incident.
A female employee was killed at the station by her partner, who then died in the blaze he set.
Fuiavailili Fa'au Gago is a camera operator for the Loabay social media group.
The company was the focus of an inquiry by the Samoa Media Council over the incident.
It was asked to pay $US400 in compensation to the Samoa Journalist Association.
The defendant also pleaded guilty to separate charges related to a domestic violence incident involving his wife.