A 17-year-old North Carolina girl who recorded a livestream of a shooting that killed three people at a San Diego Mosque and disseminated the attackers’ white supremacist writings has been charged with murder by aiding and abetting.

Forsyth County District Attorney Jim O’Neill said at a news conference in Winston-Salem that the girl, identified in court records as Sarah Lindsey Santiago, was arrested last week. A grand jury indicted her on three counts of murder and one count of conspiracy.

Under North Carolina law, the aiding-and-abetting charges carry the same penalties as if the girl had committed the attack herself, O’Neill said.

According to the indictment, Santiago agreed prior to the attack that she would record the livestream, distribute it and release a document written by the attackers. She carried out those tasks, it said, and she purchased a patch bearing a white supremacist symbol and sent it to one of the gunmen to wear during the attack.

“The individual here, locally, was the person who was recording the livestream,” O’Neill said. “She disseminated that information and she published their manifesto.”

Cain Clark, 17, and Caleb Vazquez, 18, stormed the Islamic Center on May 18 before being driven back outside by a security guard who exchanged gunfire with them as he initiated a lockdown, helping to protect 140 children who were just steps away.

Abdullah and two worshippers – Mansour Kaziha and Nader Awad, who drew the attentions of the shooters in a parking lot – were fatally shot.

San Diego Police Chief Scott Wahl previously described Abdullah’s actions as “heroic”, saying they had “undoubtedly” saved lives.

According to investigators, the shooters recorded the attack using cameras mounted on GoPro-style helmets. O’Neill said the pair had also planned further attacks “at a local Jewish temple and finally at a predominantly African American high school”.

Authorities said the teenagers had an arsenal of around 30 guns and a crossbow, which investigators say were taken from one of the shooter’s parents.

The attackers also left behind writings containing racist and antisemitic views, as well as references to white supremacist ideologies.

The document, which was reviewed by the BBC’s US news partner CBS News, pointed to a gunman who murdered 51 people at two mosques in Christchurch, New Zealand, in 2019, as one of their models.