The New Zealander shot dead in the Philippines last week, Simon Rawlinson, was embroiled in a dispute with local government figures, according to local news sources.
The 63-year-old was gunned down by a man on the back of a motorcycle in the town of Naval on Biliran island last Wednesday.
Two men, the suspected gunman and lookout, have been arrested, while the motorcycle driver is still at large.
The assailants took his bag, a laptop and documents.
Philippines Lifestyle News has reported that it has obtained a letter sent by Rawlinson to the Ombudsman, which describes his legal disputes and the friction between him and local government figures.
While there is no evidence that any of these issues were related to his assassination, the letter paints a poignant picture of a man finding himself apparently shunned and despised by his local community, Philippines Lifestyle News said.
In it, he counters a number of allegations against him, including that he "hurled" a stone, "boxed" a boy and splashed him with chlorine, "barricaded" a barangay (district) road and was a "transient". Using highly legalistic language, and citing international law, he refutes these accusations.
He also takes issue with a decision to declare him "persona non grata" and have him "ousted" by police. Again, citing international law such as the "Vienna Convention on Diplomatic Relations", he argues that this is unlawful.
The letter also shines a light on how his relations with village officials had deteriorated beyond repair.
On one occasion, he clashed with a councillor over the installation of a fence on his property. The encounter ends with the official telling him to "go home to New Zealand".
On another occasion, he clashed with a captain while moving stones on the beach, which he says was "belated" clean-up work following Cyclone Yolanda. This encounter culminates with the captain telling him to "get f.....".
The letter also reveals that local authorities had circulated a petition containing allegations against Mr Rawlinson, which had been signed by many of his neighbours. Details of the petition are not known.
In conclusion, Mr Rawlinson calls for the wholesale sacking of officials - whom he describes as "people of such detestable behaviour" - adding that the captain should be "heavily sanctioned" as punishment.
Rawlinson, a long-time resident of nearby Maripipi island, was in Naval for a trip to the market when attacked.
A witness led police to the alleged gunman's house, where they found a pistol, bullets and clothes the suspect was seen wearing on CCTV footage.
The motorcycle driver is still at large.
The Ministry of Foreign Affairs and Trade has confirmed the New Zealand Embassy in Manila is in contact with Philippines authorities over the shooting.
"Due to privacy considerations we are unable to provide any further information," a spokesperson said.
A friend of Rawlinson's said she and her partner had been left devastated by the killing.
Celia wrote on the Philippines Lifestyle News that Rawlinson was seeking to lead a peaceful life on his block and loved his adopted country.
"My partner and I were friends of Simon and are devastated by this murder.
"He loved the Philippines and felt that he was at home there despite being a New Zealand citizen."
It's the third killing of a foreigner on the island by gunmen riding on motorcycles in the space of 12 months.
Last June a 74-year-old Dutch businessman was shot by a pillion passenger. His 11-year-old son was wounded but survived.
In March a former US marine was killed by motorcycle-riding gunmen.
Those killed in previous deaths were driving their own vehicles when they were targeted.