Leonora Jane Cillay's silver Hyundai Sonata revved up a boat ramp along the shoreline, witnesses say, and plummeted into the water.
Vodka bottles and beer cans floated from the car into Jordan Lake in Chatham County, North Carolina. A bystander told officers he jumped in and tried to reach the driver through the sunroof but that she closed it on his arm.
Then, a young boy stuck his hand out of a shattered rear window.
The account comes from an incident report that suggests that Cillay, a 41-year-old mother from Cary, was concerned that an "organisation" was targeting her son, telling authorities that "this was the best option".
She directed investigators to her blog, where she has apparently written about her fears - and attempted to explain why she worries her young son is a target.
Bystanders pulled Cillay and her son from the water on May 15 and paramedics transported the two to a nearby hospital.
Authorities told NBC affiliate WRAL that the boy was treated at UNC Hospitals in Chapel Hill and released.
Cillay was later arrested by North Carolina State Bureau of Investigation agents and charged late last week with attempted murder.
Park ranger Erin Brown said she saw the boy, wearing soaking-wet pants and a long-sleeved shirt.
"I bent down and asked him his name," Brown wrote in her report. "He just stared at me and didn't say anything to me. I asked him if he was okay and if anything hurt - he just stared at me and didn't say anything."
Authorities say the boy is 6 years old; Cillay's blog says he is 5.
Brown said in the report that when she picked the boy up, he started crying and his mother started screaming, "I want my son, I want my son".
Rangers said Cillay was making strange statements and demanding that first responders remove their sunglasses and look her in the eyes.
"She kept saying, 'Look me in the eyes. I need to connect with people - look me in the eyes,' " Brown wrote in her report. "She asked me, 'Do you know how much I love my son?' I asked her, 'How much do you love your son?'
"She said, 'I love my son.' "
Brown said she asked Cillay whether her son could speak and she said no.
Authorities recovered a silver-coloured box from the scene that contained money, passports, Social Security cards and an electronic device that measures radio and microwave frequencies, according to the incident report.
A suicide note was found near a restroom, according to the rangers. In it, they say, Cillay wrote that "this is the best I can do for" the boy.
She added: "I will always love him."
The first-person blog, "Danger in a Safe Place," talks about Cillay's rough upbringing in London, saying she turned to "drinking and then self-harming" and was diagnosed with borderline personality disorder.
The blog says Cillay was concerned about her son, including his speech delays, claiming he was eventually assessed as having "sensory processing disorder and difficulties with motor planning" and put in therapy.
She also worried because he was short for his age, according to the blog; eventually, she started researching "dangers of electromagnetic radiation" and how it can impact bone growth.
The blog talks about how Cillay feared a terrorist attack and the Ebola virus - and wondered whether her son was at risk of a biochemical attack at her school.
Authorities have not confirmed whether any information in the blog is reliable.
Shannon O'Toole, a spokesman for the State Bureau of Investigation, said in an email that the agency is aware of Cillay's blog and will present any findings to the Chatham County District Attorney's Office.
Cillay is scheduled to appear in district court on June 7.
• Lifeline: 0800 543 354 (available 24/7)
• Suicide Crisis Helpline: 0508 828 865 (0508 TAUTOKO) (available 24/7)
• Youth services: (06) 3555 906 (Palmerston North and Levin)
• Youthline: 0800 376 633
• Kidsline: 0800 543 754 (available 24/7)
• Whatsup: 0800 942 8787 (1pm to 11pm)
• Depression helpline: 0800 111 757 (available 24/7)
• Samaritans: 0800 726 666 (available 24/7)
If it is an emergency and you feel like you or someone else is at risk, call 111.