A high school honor roll student encouraged her friend to kill himself before raising thousands of dollars for suicide prevention, according to authorities.

Michelle Carter, 18, has been charged with involuntary manslaughter in the death of Conrad Roy III, who died of carbon monoxide poisoning in his idling truck in Fairhaven, Massachusetts last July.

When Roy texted Carter that he wasn't sure he should take his life and had climbed out of the vehicle, she allegedly texted him: 'Get back in.'

Carter, who was 17 at the time of Roy's suicide, was indicted on February 5 and arraigned on an involuntary manslaughter charge the next day in New Bedford Juvenile Court.

The high school senior was charged as a youthful offender, which means her case is open and she could face punishment as an adult if convicted. She is free on bail and is due back in court in April.

Accused: Michelle Conrad, pictured left, allegedly knew that her friend Conrad Roy III, right, was suicidal but rather than seeking help, she encouraged him to take his life in the minutes before he died last July

Police and prosecutors say Carter, of Plainville, texted back-and-forth with Conrad before he took his life in the parking lot of a Fairhaven Kmart on July 13, 2014.

Court documents show the two friends exchanged more than 1,000 text messages in the days leading up to his death, the Fairhaven Neighborhood News reported.

Before his suicide, Conrad told her he was scared and not ready to leave his family, according to a police report, but 'she continued to encourage him to take his own life', theSun Chronicle reported.

'When he actually started to carry out the act, he got scared again and exited his truck, but instead of telling him to stay out of the truck ... Carter told him to "get back in",' the police report said.

His body was found in the truck after his parents reported him missing, and police found the text messages after looking through his phone.

Gregg Miliote, a spokesperson for Bristol County District Attorney Quinn, said in a statement on Thursday that Carter knew he was having suicidal thoughts.

Tribute: In the hours after he was found dead, Carter shared this message to her Twitter page

'Duplicitous': Three days after she allegedly encouraged him to take his life, she questioned why he had died

Cold: She also shared messages calling for suicide prevention, while paying tribute to her friend

'Instead of attempting to assist him or notify his family or school officials, Ms. Carter is alleged to have strongly influenced his decision to take his own life, encouraged him to commit suicide and guided him in his engagement of activities which led to his death,' Miliote said.

Quinn will not be overseeing the case because he knows the girl's family, he added.

After the death, Carter, who attends King Philip Regional High School, started raising money and awareness for suicide prevention and organized a fundraising softball tournament last September.

In a description for the event, 'Homers for Conrad', Carter wrote: 'Life can be tough, but helping others makes it easier.'

She later wrote on Twitter that the event had raised $2,300.

Carter has also repeatedly posted online about how much she misses her friend.

'Such a beautiful soul gone too soon,' she wrote on the day of his death. 'I'll always remember your bright light and smile. You'll forever be in my heart, I love you Conrad.'

Most recently, just two days before her arraignment, she shared this image of Conrad, adding: 'Really missing you tonight'. She is free on bail but has been ordered not to touch her social media pages

Victim: Roy, 18, was a boat captain at his father's company and was about to start college when he died

Three days later, she added: 'I will never understand why this had to happen.'

'1 month without your goofy humor and genuine love,' she later wrote. 'I miss you every day. I hope you're finally happy up there Co.'

On September 10, 2014, she posted: 'National Suicide Awareness day, I wish more people understood. I love you and miss you everyday Conrad. Help others #WeCanEndSuicide.'

Her most recent message - written just two days before her indictment - reads: 'Enjoy the parade from up there tomorrow Conrad, I know you would of loved to be there ♥ Really missing you tonight.'

As conditions of her bail, she is not allowed to use the internet or social media and cannot text anyone but her parents.

She is due back in court for a pretrial hearing on April 17.

According to The Plainville Times, the teenager was also a founding member of 'Connect-To-Cure', a fundraiser selling $10 bracelets to raise funds for cancer patients at Boston Children's Hospital.

Three weeks after she was arraigned, she went to the hospital to take part in a charity event.

Her lawyer told The Standard Times that Carter did not commit a crime and expects the charge to be dismissed.

Free: Carter, a high school senior who's on the honor role, has been charged as a youthful offender, which means her case is open and she could face punishment as an adult if convicted

'I can't understand why they brought the charge,' Joseph P. Cataldo said. 'They're trying to claim there is manslaughter, when they freely admit the boy took his own life. You can't have it both ways.'

King Philip Regional School District declined to comment on the case.

'The circumstances surrounding this tragic loss are under investigation,' Superintendent Elizabeth Zielinski told CBS Boston. 'Our deepest sympathy is extended to the family and school community of Conrad Roy.'

Conrad Roy had graduated from Old Rochester Regional High School, where he was an all-around athlete who played baseball, rowed crew and ran track, according to an obituary.

He had earned his captain's license from Northeast Maritime Institute and worked for his family's marine salvage business. He was planning to attend Fitchburg State University.