31-year-old Jennifer I. Schneider went missing September 13 in Waukegan and was found dead Wednesday. | Provided photo.

A missing 31-year-old woman, who had mental illness, was found dead in a forest preserve in Waukegan on Wednesday, officials said.

Jennifer I. Schneider, 31, was last seen on September 13 around 7:15 a.m. when she left her parent’s home in Waukegan for a meeting in Aurora.

Her father’s 9mm pistol also went missing when she disappeared and her phone had been turned off, the woman’s family said.

Schneider’s car, a black Honda CR-V with Colorado plates, was found in the main parking lot of Lyons Woods Forest Preserve, 10200 Blanchard Road in Waukegan, when the park was closing for the night.

Following extensive searches of the Lyons Woods Forest Preserve, police found her body on Wednesday, Lake County Coroner Dr. Howard Cooper confirmed.

“Mr. and Mrs. Schneider appreciate all the love and support the community has shown by sharing the post to find her, and everyone’s willingness to volunteer during the search. Thank you, everyone,” Val Smith, a family friend, said.

[Suggested Article]  $2 million bond for man charged with soliciting child on social media, sexually abusing her in Waukegan

“The Schneiders want to thank how amazing and fantastic all the law enforcement were in collaborating together to help find Jennifer,” Smith added.

A 13-page letter, along with a power of attorney and living will, was found on Schneider’s laptop at her home. The letter, addressed to her family, detailed Schneider’s struggle with mental illness, the mental health system in the United States, the world, corporations and other topics.

We are here. This is happening, and I am sorry. However, I needed to make this decision. Essentially, borderline personality disorder—along with my many other mental illnesses, which include clinical depression, treatment resistant depression, dysthymia (yes, that’s three varieties of depression), generalized anxiety disorder, social anxiety disorder, post-traumatic stress disorder, and avoidant/dependent personality disorder—has had and will continue to have a large, negative impact on my life,” Schneider said in the opening of the letter.

[Suggested Article]  2 suspects armed with guns arrested after shot fired during home invasion in Gurnee prompts school lockdowns

I have made the decision to no longer live with a brain ravaged by borderline personality disorder and my long list of additional mental illnesses. Simply put, it is too painful for me to exist with all of these mental illnesses,” Schneider said in the letter.

I understand that there are treatments for borderline personality disorder and all of my other mental illnesses, but I’ve already been through over six years of treatment. For years and years, I was in treatment with little to no results, just suffering. Like with some forms of cancer, treatment for some mental illnesses can only do so much. I want the suffering to end,” Schneider said.

An autopsy is being scheduled by the Lake County Coroner’s Office.