"The District Attorney's Office has examined the investigation of the Birmingham Police Department and the evidence collected by BPD," Anderton said in a statement. "They have talked with many of the students in the school, in the classroom where the shooting took place and collected evidence from the scene."
Based on that evidence, warrants were issued for Barber’s arrest, Anderton said.
"Our hearts go out to the family of Ms. Arrington, all of her friends and those whose lives would have been changed through her nursing dreams had this event not occurred," Anderton said. "This is a parent's worst nightmare. We expect the charges will be heard through the court system and justice meted out to the person responsible."
No motive for the shooting has been released. Anderton said on Friday, however, that his office “stands strong with the Huffman High School Vikings, the Birmingham school board and the Birmingham Police Department in denouncing the continued use of firearms by anyone to settle disputes.”
"This is especially true for the students of our county, where they should be and feel safe in the learning environment of a school," Anderton said.
It was unclear if there was a dispute between Barber, a junior and wide receiver for the Huffman High Vikings, and Arrington.
AL.com reported that Birmingham City Schools Superintendent Lisa Herring acknowledged Thursday that Huffman High has two working metal detectors, but that the devices were not in use the day of the shooting. Herring said she has already requested additional metal detectors for the school district.
The school also had three school resource officers on campus Wednesday, but their whereabouts when the shots were fired have not been made public, AL.com said.
Police investigators initially believed the shooting to possibly have been accidental since Barber was also injured, but they began to question that idea after viewing video recorded of the incident. The source of that video has not been made public.
As the investigation progressed, detectives took Barber, who suffered a self-inflicted gunshot wound to the leg, into custody as a person of interest. Barber, who had been held in the Birmingham City Jail since being released from the hospital, was moved Friday to the Jefferson County Jail, where his bail had been set at $75,300.
He was apparently bailed out of the county jail Friday afternoon. A woman named Makiya Barber, who identified herself as Michael Barber's sister, posted a photo on Facebook that showed him in street clothes, sitting in the backseat of a car.
A photo filter put flower crowns on the siblings’ heads as they mugged for the camera.
"Out the big ole gate!" Makiya Barber wrote. "Y'all can stop the fake friend request(s) now. God still gotta plan for the kid!"
[The social media post was made private after the publication of this article.]
In previous posts, Makiya Barber argued that the shooting that killed Arrington was an accident.
"And what y'all NOT about to do is make my brother out to be this horrible unparented child," she wrote in one post. "All the he say, she say ... we have the facts!
“Rest in peace, baby girl, and my brother is gonna come out stronger and wiser.”
Another post pointed out the fact that detectives have footage of the shooting.
“The police have footage and facts, so the countdown to see my brother is on! Mike Mike, I know you hungry!”
The post included several hashtags, including one offering prayers for the Arrington family and one that stated, “Everything for a reason.”
Arrington, who was due to graduate in two months, had already been accepted into college, where she planned to study nursing. Her Facebook page, which has since been turned into a memorial page, includes an introduction that reads, "SEN18R. Dream come true, gotta chase it. Future RN."
Her last photo that she posted of herself appeared to be taken in the hallway of the school. It was posted the day before she was killed.
Her photos also include images of her wearing scrubs.
During a news conference held inside the school Wednesday night, Birmingham Mayor Randall Woodfin spoke of the grief of losing a girl with a bright future.
“I know that there’s an active investigation going on, but I just want to remind all of us we lost a person today, and not just a person, a student,” Woodfin said. “But I’m quickly reminded this is not just a student, this is someone’s daughter. Someone’s niece. Someone’s best friend. Someone’s granddaughter we lost.
“This is a 17-year-old who, 30 days from now, would be 18. A graduating senior who had been accepted into college already, who had aspirations and dreams to be a nurse. So, we’re not just talking about some person. We’re talking about losing a part of our future. And our hearts are heavy.”
Herring kept Huffman High closed on Thursday, but the school’s doors reopened to students, faculty and staff Friday. The night of the shooting, she described Arrington as “one of (the district’s) brightest and best scholars.”
She told AL.com that Birmingham students will honor Arrington during the National School Walkout next Wednesday. They will stand outside for 18 minutes instead of 17, adding Arrington to the 17 students killed on Valentine's Day at Marjory Stoneman Douglas High School in Parkland, Florida.