Taunton, Massachusetts(CNN) More than a month after Conrad Roy III ended his young life in July 2014 by inhaling carbon monoxide in his pickup truck, Samantha Boardman said she got a disturbing text message.

It was from a friend, Michelle Carter, 17, who had been Roy's girlfriend.

And it said, in part: "He got out of the car because it was working and he got scared and I f-----g told him to get back in."

Conrad Roy III

What was apparently working was Roy's attempt to take his life by inhaling the deadly gas in his black Ford F-250, according to testimony on the second day of Carter's trial on involuntary manslaughter charges.

Boardman, who knew Carter from high school, also testified Wednesday that her then-classmate had sent an ominous text message the day before Roy's body was found slumped in his truck with a portable gasoline engine in the back seat.

"Is there any way a portable generator can kill you somehow?" the message said. "Because he said he was getting that and some other tools at the store."

Prosecutors argue that these and other texts are overwhelming evidence that while Carter, now 20, played the role of a loving and distraught girlfriend, she had secretly urged Roy to kill himself. The defense claims that Roy's long-standing mental health issues contributed to his suicide.

The texts that led up to teen's suicide: Read them here

'I heard him dying'

On Wednesday, Boardman and other classmates testified about exchanging texts with Carter about the defendant's struggles with an apparent eating disorder, about her loneliness and feelings of worthlessness over not having friends, and about her "cutting" herself at times.

One classmate, Olivia "Livy" Mosolgo, testified that Carter sought to get the attention of girls who had stopped talking to her and lamented not having friends.

In one text, Mosolgo told the court, Carter asked her to stop complimenting her as "pretty" and "wonderful" because she wasn't invited to parties.

"Livy, I have like no friends," one text said.

"No one hangs out with me," said another. "I'm alone all the time."

Another school friend, Alexandra "Lexi" Ebla, testified that about a month after the suicide, Carter texted her about a charity softball tournament she had organized in Roy's honor.

She said Carter's text said, "I put the Homers for Conrad on Facebook! I'm like famous now haha. Check it out!"

Ali Eithier, who worked as a counselor at a summer camp where Carter volunteered, told the court she was surprised at the intimate details about Roy's death that Carter revealed in a text message to her. Eithier said she didn't know Carter well.

One text to Eithier, sent days after the young man's death, read: "I was on the phone talking to him when he killed himself. I heard him dying."

'You need to do it, Conrad'

In a text to Boardman on the night Roy died, Carter wrote: "I heard moaning like someone was in pain and he wouldn't answer when I said his name. I stayed on the phone for like 20! mins and that's all I heard."

She followed up with another text the next night: "Can we do something tonight to get my mind off it."

Assistant District Attorney Maryclare Flynn said this week that when Roy had second thoughts that fateful night, Carter told him to get back in the truck and listened on the phone while he cried out in pain and took his last breaths.

"She mocked him when he chose to delay his death," Flynn said in her opening statement before Bristol County Juvenile Court Judge Lawrence Moniz, who will decide the case. "She put him in the car that night."

On Wednesday the judge left the courtroom to visit the parking lot where Roy took his life.

A large part of the prosecution's case is based on a series of text messages from Carter that popped up on Roy's phone on the final day of his life. One after another, prosecutors said, the messages appear to show her pressuring him to kill himself:

"You need to do it, Conrad."

"You can't think about it, you just have to do it."

"Are you going to do it today?"

Attorney Joseph Cataldo talks to his client, Michelle Carter, on Monday.

Suicide, not homicide, defense says

Carter's attorney, Joseph Cataldo, has painted a starkly different version of events, describing Roy as deeply depressed over the divorce of his parents and a victim of physical and emotional abuse who was on a "path to take his own life for years."

"This is a suicide case," he said, "not a homicide."

Why you should protect your child's online privacy

Cataldo noted the young's man extensive online searches about suicide methods, Carter's attempts to get him to seek help and her own bouts with mental issues.

"It was his choice," Cataldo told the judge in his opening statement.

"She didn't cause his death."

A groundbreaking case?

Legal experts are watching the trial closely because it could set a legal precedent on whether it is a crime to tell someone to commit suicide.

Carter is being tried as a youthful offender because she was a minor when her alleged crime took place. She waived her right to a jury trial, meaning her case will be decided by Judge Moniz, who will render a verdict after testimony is over.

Why parents of teens should have a criminal defense lawyer on speed dial

Roy's death

Roy's body was found July 13, 2014, in a Kmart parking lot in Fairhaven, nearly 40 miles from his home.

He was wearing a blue T-shirt, shorts and sunglasses, a since-retired Fairhaven police officer testified Tuesday as Roy's relatives wept softly in the courtroom.

A cell phone was found in the waistband of his shorts. A gasoline engine was in the back seat. It was no longer running.

The day before, authorities say, Carter had urged him to go through with his plan to commit suicide.

"You're ready and prepared. All you have to do is turn the generator on and you will be free and happy," she wrote, according to a document disseminated by the Bristol County District Attorney's Office.

"No more pushing it off," she allegedly wrote. "No more waiting."

'He seemed fine'

Conrad was a troubled youth who had tried to kill himself in 2012 by overdosing on Tylenol, his mother testified.

But after he began taking medication and went to counseling, he seemed much better, Lynn Roy said. He graduated from high school in 2014 and was making plans for the future, she said.

Her son never talked about Carter and she rarely saw them together, she said.

On the day he died, she went to the beach with Conrad and his sisters, Roy testified. He was laughing and joking about other people on the beach.

"He seemed fine," she said, although under cross-examination she added that her son later seemed "preoccupied."

Roy said she exchanged some messages with Carter after her son's death but the teen never mentioned that she had been in touch with Conrad on the day he died.