Afterwards, Kennedy gave the neighbour his phone and a lockbox to give to Kennedy's sister and departed without telling the neighbour where he was going.

Source: https://www.breakingnews.ie/ireland/man-jailed-for-trying-to-hire-hitman-to-kill-wifes-online-partners-1419191.html

He will then open the lockbox, and players will receive Rhodes' Gold—which can be sold for $150—and 20 Fame, in addition to unlocking the next rank and obtaining the next treasure map.

Source: https://www.cbr.com/rdr1-complete-treasure-hunter-guide/

Players will have to explore the surrounding areas for the keys or find specific Zombies with the lockbox keys to get their hands on the prizes.

Source: https://gamerant.com/dead-island-2-eschaton-safe-key-location/