Three 16-year-old girls have been charged in the killing of a classmate during a fight in the bathroom of a Delaware high school

Three high school girls in Delaware are facing criminal charges over the fatal beating of a classmate inside a school bathroom last month, authorities said on Monday.

Amy Joyner-Francis, a 16-year-old sophomore at Howard High School of Technology in Wilmington, Delaware, died following an early-morning fight on April 22.

The state Department of Justice said it had charged Trinity Carr, 16, with criminally negligent homicide and would seek to have her tried as an adult. She faces up to eight years in prison.

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This is the horrific moment high school teen Amy Joyner was allegedly beaten to death by a group of bullies in the school bathrooms

Amy Inita Joyner-Francis (left and right), 16, died after being attacked by Trinity Carr, Zion Snow and Chakeira Wright, all 16, in the women's bathroom at Howard High School of Technology in Wilmington, Delaware, Thursday morning

Carr was the only girl to strike Amy, though all three girls planned the confrontation, according to the department.

The other two girls, Zion Snow and Chakeira Wright, have been charged with criminal conspiracy, which carries up to one year in prison. They will be tried as juveniles.

An autopsy concluded that Joyner-Francis died from a 'cardiac incident' that stemmed from a pre-existing heart condition but was brought on by the stress of the attack, according to the department.

'The cardiac incident would not have occurred if she had not been assaulted,' the Department of Justice said in a statement.

It was not immediately known whether the three defendants had been arrested or had retained defense lawyers. 

The fight broke out around 8.15am on April 22 before classes at Howard High School of Technology.

Students who witnessed the deadly scuffle said that Joyner and another girl started fighting in one of the women's bathrooms over a boy, when a gang of other girls jumped the victim.

At one point, someone slammed her head against a sink, according to witnesses who spoke with 6ABC. 

Joyner-Francis was flown to A.I. DuPont Children's Hospital in critical condition, where she was later pronounced dead. The cause of death has not been confirmed

Authorities questioned Carr, Snow and Wright over the deadly brawl - all of whom have now been suspended from school.

'Now they know they're in very serious trouble and could spend a substantial amount of time in prison,' Mayor Dennis Williams told CBS News. 

Paramedics (pictured) wheeled the student out of the school. Medics performed CPR on the victim before a helicopter arrived to transport her to a hospital 

Amy was flown by helicopter to A.I. DuPont Children's Hospital in critical condition. She was later pronounced dead at the hospital

'My heart bleeds for the family,' Mayor Dennis Williams told a news conference. 

Kaya Wilson was in a stall when the fight broke out and spoke with the local news station after leaving school. 

'She was fighting a girl, and then that's when all these other girls started banking her -like jumping her - and she hit her head on the sink,' Wilson said.

'There was an altercation that initially started between two people, and my understanding is that additional individuals joined in against the one person,' Gary Fullman, chief of staff to the Wilmington mayor, told KTLA. 

Speaking a day after her shocking death, her father Sonny Francis told FOX29: 'I thought schools were a safe place.

He added: 'I think this is a dream and I'm trying to wake up. All I know is my daughter is gone. She was the love of my life and it hurts.' 

Sherry Dorsey Walker, a Wilmington city councilwoman, said that the family is asking for spiritual healing in the community and no retaliation. She says they're also 'asking people to just be calm and pray for them'.

Two female students are being interviewed by police, a spokesman for Wilmington's mayor confirmed  

The cause of the death for the student is still unknown. Above, a crime scene vehicle at the school on Thursday

Mayor Dennis William was emotional as he announced Joyner-Francis' death. He said: 'My heart bleeds for the family'

The councilwoman described the victim as 'a wonderful human being', adding that 'her loss is a big void, not just in the family'. 

Nathaniel Kenyatta, a freshman at the school, was friends with the victim and spoke to Delaware Online on Thursday.

He says he met her in a HVAC class and that she was an easy person to talk to.

'She was very open,' he said. 'I feel bad for the people who have known her for years.' 

Her friends and neighbors knew her as the quiet teen who would focus on her homework.

Nik Stryminski told the News-Journal that Amy had kept him safe and out of a fight earlier this school year.

When he and another student were getting ready to fight she stepped in, backed him into a corner and calmed him down.

He said: 'She didn't believe in fighting, and the craziest thing is she died in a fight.'

Stryminski believes Joyner-Francis went into the bathroom not to fight but to 'talk things out'.

Troy Johnson, a sophomore at Howard, said Amy was a good influence to her peers with her calm personality, he said.

'If I were to have kids I'd want them to hang around someone like her,' he told the News Journal.

Another student said Amy was often the one who calmly counseled her friends.

Amil Gibbs, a sophomore at Howard, told the News-Journal that she would sit with Amy during lunch and tell her about problems she had in school. And Amy would encourage her to 'be strong'. 

From Twitter to Facebook #RIPAmy was trending last week as several people across the nation have called her death senseless.

Actress Paige Hurd tweeted that she is 'hurt' by the loss of such a young life and her 'heart is so heavy for her and her family' 

Another user tweeted about the plight of a world where a teenager 'gets murdered by her classmates in a school bathroom while other classmates record it'

Some said the worst part about Amy's senseless death is to know that 'we won't learn from this'  

And others are calling for justice to be served against the girls who are responsible for Amy's death 

On social media, many say they can't believe other students didn't intervene to help her. 

Others said it's sickening to know that students stood there and watched and recorded as the fight erupted all because of a boy. 

One Twitter user said she prays 'for this generation' and hopes 'justice will be served', while another said the world needs a 'cultural shift'. 

Howard isn't known as a violent school and Police Chief Cummings said he did not know of any other problems in recent days.

Superintendent Victoria Gehrt called Amy's death an 'unbelievable tragedy for the family'. She also said that despite what happened, Howard High School of Technology 'is a safe school for our students'. 

A student cries in front of Howard High School of Technology on Thursday after a city official announced a student had died after the confrontation inside the school

Classes were cancelled at the vocational school on Thursday after the deadly attack. It's still unclear whether school will reopen on Friday