The pair, who had been dating for about six weeks, were at a party at Kwitzil Lake on May 18, 2014, when Moore said she wasn't feeling well and asked to sleep in the back of Wood's car.
According to the report, Wood was reminded Moore was in the back, but got behind the wheel and drove the car into the lake, drowning both of them.
The coroner found Wood had a depressive tendencies and had expressed suicidal thoughts earlier that night.
A toxicology report showed Moore and Wood had alcohol and ecstasy, or MDMA, in their systems and Wood had also taken cocaine.
"It's the worst feeling in the world and I wouldn't want any parent to go through this," said Wood's mother Laura, speaking publicly for the first time since her son's death.
Drugs could have caused 'impulsive behaviour'
The coroner's report said the drugs could have affected Wood's mental state, specifying, "Cocaine and alcohol produces the chemical cocaethylene, which produces euphoric effects.
"Given that MDMA was also used and also produces euphoric and hallucinogenic effects, the combination of these drugs would reduce inhibitions and contribute to impulsive behaviour."
Wood said she had a "hunch" her son was using drugs, but was surprised by the toxicology results. Even after reading the full report, she doesn't believe her son was depressed.
"I wish there was more awareness of what the drugs and mixing of the drugs can do to your child — along with alcohol, along with how they're feeling," she said.
This grad season, Wood is cautioning other parents to watch their children for signs of drug use, and said she is starting to talk more about drugs with her other two children in light of the report.