Both of the suspects in the deadly shooting at a Colorado charter school were students at the school but weren't on law enforcement's radar as a possible threat, authorities said. Police said 18-year-old Devon Erickson and another student started shooting inside classrooms at STEM School Highlands Ranch Tuesday afternoon.

Devon Erickson, 18, looks up from the defense table during a court appearance in Castle Rock, Colorado, May 8, 2019. CBS Denver

Erickson appeared in court Wednesday. The other suspect appeared later that day. The defendant was listed in court records as 16-year-old Maya McKinney, according to The Associated Press.

A public defender assigned to McKinney says his client goes by Alec and uses male pronouns. McKinney is being held on suspicion of murder and attempted murder.

District attorney George Brauchler says he hasn't decided whether to file adult charges. He says McKinney is the youngest age at which Colorado law allows prosecutors to file adult charges without a judge's review.

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McKinney is due back in court Friday.

Erickson hung his head for most of his hearing, his face covered by a mop of dark and pink hair. He would nod or shake his head in response to questions, but he told the judge "no" when she asked him if he had any questions.

According to witnesses, senior Kendrick Castillo, 18, was shot trying to stop one of the shooters inside the school and died from his wounds, CBS News correspondent David Begnaud reports. Eight others were wounded in the shooting.

Douglas County Sheriff Tony Spurlock said neither Erickson nor the other suspect was known by law enforcement to be a threat to the community. Police searched Erickson's home Tuesday, and they towed a vehicle away from a garage.

High school student Michael Schwartz claimed Erickson did, in the past, talk about causing a lot of harm and sadness. "I always thought he was just messing around and stuff, but sometimes he did hint at it here and there," Schwartz said.

Josh Dutton, 18, told the AP he saw Erickson for the first time in four years on Sunday at a light rail station but his friend from middle school didn't give the impression he wanted to talk. "He said he'd just turned 18 and he owned rifles," Dutton said.

On Wednesday morning, Spurlock told reporters neither of the suspects were of legal age to own or purchase guns. The sheriff said the suspects used at least two handguns.

Dutton told the AP his friend from middle school had changed. He said Erickson was skinnier than he remembered and he was wearing black clothes, a hat and sunglasses.