Juliette Lewis has doubts surrounding the death of her friend and August: Osage County castmate Misty Upham.

Lewis, 41, mourned her friend in posts on Twitter and Instagram and speculated that her death was criminal and not an accident nor a suicide.

“Misty Upham survived many things that many don’t early on in life. She fought for the voiceless fiercely,” Lewis wrote on Instagram alongside a photo her late friend. “She understood suffering and the deepest pain. She had a presence everyone saw and felt. It is this presence that will continue. Out of the dark space in which her light got dimmed. I will remember her as tuff. Wise. Funny. Spiritual. And hopeful. This is another great reminder to call and check on someone when you think to. Not when its too late. RIPMistyUpham.”

Upham went missing on Oct. 5. On Thursday, she was found dead by family members “at the bottom of a 150 [ft.] embankment near the White River,” according to local authorities.

Loading

Misty Upham survived many things that many don't early on in life. She fought for the voiceless feircely. She understood suffering and the deepest pain. She had a presence everyone saw and felt. It is this presence that will continue. Out of the dark space in which her light got dimmed. I will remember her as tuff. Wise. Funny. Spiritual. And hopeful. This is another great reminder to call and check on someone when you think to. Not when its too late. RIPMistyUpham

View on Instagram

Tracy Rector, filmmaker and a close friend of the Upham family, told The Hollywood Reporter on Friday that Misty’s father Charles identified his daughter’s body to police. Charles initially believed his daughter — who suffered from bipolar disorder — could have been suicidal after not taking her medication.

However, the Upham family changed their mind after seeing their daughter’s body on Thursday and believed her death was not the result of a suicide.

“The family has stated that, after seeing the body, they still do not feel that Misty Upham committed suicide,” Rector told The Hollywood Reporter.

Misty Upham survived many things that many don't early on in life. She fought for the voiceless… http://t.co/nSNYHU4vgI

— Juliette Lewis (@JulietteLewis) October 17, 2014

#RIPMistyUpham Misty spoke out alot against injustices within Native community. And had known enemies. Police must do an investigation.

— Juliette Lewis (@JulietteLewis) October 17, 2014

I cant sleep. Too much darkness. I feel so sad about Misty. I know she has more to say. And about how she died. #RIPMistyUpham

— Juliette Lewis (@JulietteLewis) October 17, 2014

All I want is a thorough investigation into MistyUpham's deathAnd Not old Native American tensions or her past emotional probs to prevent it

— Juliette Lewis (@JulietteLewis) October 17, 2014

Rector also told the website that the Upham family was upset with police for allegedly refusing to help find the missing Native-American star.

“First and foremost, the family wants everyone to know that the Auburn police did not help with this situation at all,” Rector said. “They refused to help. When she disappeared on Oct. 5, the family knew something was seriously wrong — it was out of character for her to be gone so long without being in touch — and they repeatedly went to the police, who insisted there was no cause for concern.”

Lewis also retweeted a few seemingly sinister messages Upham posted on Twitter in the days leading up to her friend’s disappearance.

Indian Trader just followed me. Please everybody, alter your speech. Censor yourself and walk on eggshells so not to hurt their feelings…

— Misty Upham (@MistyUpham) September 29, 2014

Barbaric. Little bird I found tied by it's leg on Muckleshoot reservation. pic.twitter.com/I5pWYk1pC7

— Misty Upham (@MistyUpham) October 1, 2014