PLAINVILLE, Mass. (WPRI) — Prosecutors say a Massachusetts teen “wantonly and recklessly” assisted her friend in taking his own life last July – and new court documents are shedding light on how she allegedly encouraged him to commit suicide.

Michelle Carter, now 18, is charged with involuntary manslaughter in the death of 18-year-old Conrad Roy III. He died of carbon monoxide poisoning last July and was found in his truck behind a Fairhaven K-Mart, police said.

Newly-released text messages – obtained by Eyewitness News – prove that Carter caused Conrad’s death, according to prosecutors.

Prosecutors say Carter, who was 17 at the time of Conrad’s death, first counseled him to overcome his doubts – telling him he would be happier once he was dead and that his parents would not suffer.

The documents detail the text message conversation between Carter and Conrad, in which she says: “I love you to the moon and back and deeper that the ocean and higher than the pines, too, babe forever and always. It’s painless and quick,” referring to carbon monoxide poisoning.

She then writes: “You said your mom saw a suicide thing on your computer and she didn’t say anything. I think she knows it’s on your mind and she’s prepared for it. Everyone will be sad for a while but they will get over it and move on.”

Conrad responds: “Aww. Thank you, Michelle.”

Prosecutors allege that Carter devised a plan to run a combustion engine within his truck to poison him with carbon monoxide. Officials say she went as far as to pressure Conrad into committing suicide – questioning why he hadn’t done it already.

Carter: “You can’t think about it. You just have to do it. You said you were gonna do it. Like I don’t get why you aren’t.”Conrad: “I don’t get it either. I don’t know.”Carter: “So I guess you aren’t gonna do it then. All that for nothing. I’m just confused. Like you were so ready and determined.”Conrad: “I am gonna eventually. I really don’t know what I’m waiting for but I have everything lined up.”Carter: “No, you’re not, Conrad. Last night was it. You kept pushing it off and you say you’ll do it, but you never do. It’s always gonna be that way if you don’t take action. You’re just making it harder on yourself by pushing it off. You just have to do it.”

Conrad took his own life on July 13, according to police. Prosecutors say he called Carter and got out of his truck because the gas was working and he was scared.

Prosecutors say Carter told him to get back in.

Carter’s lawyer argues that encouraging someone to commit suicide is not illegal under Massachusetts law.UPDATE: Carter’s attorney filed a motion to dismiss the manslaughter charge against her on Monday, which is now being considered by a judge.