Sam's mother died in 1989 when Sam was six. 
Father gone missing
Sam was arrested for a number of minor crimes, including drunk and disorderly conduct, possession of drugs, and assault. 
At some point, Sam stole his father's identity and started working for the Star City Electric Company. 
Discovering the truth
In 2019, after Oliver started working the SCPD, Sam hacked into the DA's office's computer and obtain the unredacted transcripts of Oliver's therapy sessions with Dr. Parker while he was incarcerated at Slabside. That was when Sam learned the truth that Oliver's father killed his.
Before learning the truth, Sam believed his father was still alive and was planning a trip to the North China Sea to search for him. 
Sam kidnapped Rich Kannon, a reporter, and forced him to make a video saying that unless Oliver quit the SCPD then "people would suffer".
Later, Sam hacked into the Star City power grid thereby causing the SCPD headquarters building to become electrified. He threatened that unless Oliver confessed to what his father did then he'd electrocute an officer to death every minute. 
After Oliver confessed to how Sam's father died, Sam threatened that unless the SCPD killed Oliver he'd kill everyone in the building. However, Dinah destroyed the machine Sam was using to control the electricity and Sam was arrested. 
Behind the scenes
- In the DC comics, Hackett is a former pilot for the Royal Air Force, Hackett eventually came into the employ of a heroin manufacturer named China White. China conducted her business from an island volcano in Fiji, and communicated her orders to Hackett from there. Over a decade ago, Hackett insinuated his way into the lifestyle of millionaire playboy Oliver Queen. He convinced Oliver to invest in several illegal offshore accounts, though Oliver was unaware that the money was being used for drug trafficking.