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CENTENNIAL, Colo. — A second Arapahoe High School security guard is raising concerns about safety nine months after a deadly shooting on campus.

A security guard posted an open letter on Facebook claiming Littleton Public Schools administrators didn’t do enough before the shooting and that safety is still a concern.

She says after she spoke up, the district put her on leave and it’s treating her like another security guard who criticized how the district handled the shooting on Dec. 13 in which student Karl Pierson opened fire inside the school, killing 17-year-old Claire Davis.

Through Facebook school security guard Christina Erbacher-Kolk says Claire’s death was preventable.

She says administrators did nothing when employees reported Pierson looked up guns on his computer after threatening to kill his speech and debate coach.

Erbacher-Kolk says the administration told her, “We all know this student will go off the deep end. It just will not happen at Arapahoe.”

She says the administration also ignored employees when she told them about cameras and doors not working properly, and requested more safety training. Erbacher-Kolk says the district has put her on leave for breaking protocol and the district has “retaliated against myself and at least one other for bringing problems like these into view.”

The other person is security guard Cameron Rust, who talked a month after the shooting and shared the same concerns.

“He threatened to kill Tracy Murphy,” Rust said. “We were just told to keep an eye out for him.”

He said even after he found Pierson looking at guns online at school, administrators told him not to document anything.

The district has not responded to the latest allegations. A few weeks ago, school records showed administrators did not consider Pierson a serious threat before the shooting.

The Arapahoe County Sheriff’s Office started an investigation in December but has not released its findings.