Cheryl Walker says that her son would have stayed at home had it not been for a single text message reminding him about an engagement.
Paul was due to attend an event for his charity Reach Out Worldwide, but had completely forgotten about it - until someone texted him to remind him.
According to People, in the doc Cheryl explains that he was in high spirits on the morning of his death, when he was sat in the kitchen with his 15-year-old daughter Meadow while on a break from filming Furious 7. They were making plans to pick out a Christmas tree and decorate it that night.
"We were having this good conversation, and he'd forgotten about an event he had," Cheryl reportedly said.
"He got a text and said 'Oh my gosh, I'm supposed to be somewhere!'"
That was when Paul reportedly rushed out of the door to the charity event, which was to help victims of Typhoon Haiyan in the Philippines.
After Paul had left the fundraiser in a car driven by his friend, financial advisor and former race-car driver Roger Rodas, the vehicle lost control and crashed into a lamppost. The car then exploded, killing both instantly.
"I think so many people think 'Oh, he was just a movie star who was killed in a car accident.' But there was so much more to him," Cheryl added.
"That was just a piece of who he was. He was an amazing man."
The documentary also features tributes from other family members, as well as Paul's friends and former colleagues.
In another clip, his sister Ashlie remembers Paul over a video of them riding on a Big Wheel tricycle together.
"He liked to go fast," she said.
"As soon as I was old enough to hang on tight, I was on the back of his Big Wheel with him going for the ride of my life."
Caleb Walker, one of his brothers, also reveals how despite being a well-known actor and celebrity, Paul would have been content without either.
"He'd always say, like, 'I wanted to be a park ranger, you know,'" Caleb said.
"Make 28-grand a year and, like, live in the wilderness. That's really what he wanted to do."
His uncle, Rhett Walker, also referred to him as a 'giver', saying: "I can actually say that he did a lot of things, that made a lot of difference, in a lot of people's lives."
I Am Paul Walker premieres on the Paramount Network on 11 August.