The Danvers teen who raped and slaughtered his high school math teacher a decade ago has pleaded guilty to the attempted murder of a state Department of Youth Services worker while he was in custody awaiting trial for his teacher’s murder.

Philip Chism, 25, pleaded guilty Friday in Suffolk Juvenile Court in Boston to attempted murder, assault with intent to murder, assault with a dangerous weapon and kidnapping. Judge Helen Brown-Bryant sentenced Chism to 17 to 20 years in state prison to run concurrent with his murder sentence.

His victim, a then-29-year-old female clinician at the DYS facility Chism was staying as he awaited trial, called her attacker “a true monster” who “should remain in prison for the rest of his life.”

“I remember the bruises across my face and body, around my neck; the cuts on my arm and back, the pure exhaustion from having to struggle against being assaulted. Thinking I was going to die in that bathroom,” the victim wrote in an impact statement read Friday by prosecutor David Bradley. “Although the physical bruising has long disappeared, 10 years later, I still feel this force hitting me repeatedly, reminding me that I almost lost my life to Philip Chism, a murderer.”

Danvers High School teacher Colleen Ritzer (AP Photo/Courtesy of Dale Webster via The Eagle-Tribune, File)

Chism was 14 years old when he raped and murdered Danvers High School math teacher Colleen Ritzer, an Andover woman who was just 24 years old. Evidence presented in the case shows Chism stalked Ritzer through the halls of the high school on Oct. 23, 2013, before raping her and then slashing her to death with a boxcutter in a bathroom.

He was sentenced on Feb. 26, 2016, to life in prison for Ritzer’s murder. His was the first such sentence since the Massachusetts Supreme Judicial Court eliminated a life without the possibility of parole for juvenile defenders. Based on the sentencing, Chism would be eligible for parole at age 57.

The charges to which he pleaded guilty Friday came from yet another act of violence perpetrated by Chism while in DYS custody and awaiting trial for Ritzer’s murder.

On June 2, 2014, Chism was seated at a table in an open room surrounded by a low wall at the DYS facility where he was to study since he refused to attend classes while in custody, according to prosecutor Bradley. A female clinician monitoring him left to go to the bathroom in a staff area and Chism took interest.

Chism took off his sandals to be more silent, Bradley said, and walked into the staff area holding a pencil as a weapon. When the victim exited the bathroom, he stared at her before placing his hands around her neck. He slammed her into the cinderblock wall — which is how he landed the assault with a dangerous weapon charge — as he choked her. When the woman was able to loosen one of his hands from her neck, Chism began pummeling her.

“I’m gonna kill them all,” Chism allegedly screamed repeatedly as other staffers rushed to his victim’s aid and restrained him.

Full victim impact statement

Even having to write these words makes me feel sick, unable to put together the exact pieces to explain how I feel about what happened to me in that bathroom on June 2, 2014. I’d like to say it does not have any power over me. I’d like to say that I don’t think about it off and on, a nightmare that doesn’t stop replaying or affecting my life. Most days I still feel detached from my former self. Following this horrific and terrifying event, I remember the bruises across my face and body, around my neck; the cuts on my arm and back, the pure exhaustion from having to struggle against being assaulted. Thinking I was going to die in that bathroom. Although the physical bruising has long disappeared, 10 years later, I still feel this force hitting me repeatedly, reminding me that I almost lost my life to Philip Chism, a murderer.

Immediately after the assault, I was unable to work for months, unable to leave my home for an extended amount of time, unable to use public restrooms without a supportive person being present for fear that he would be standing behind the door as I opened it each time. I remember being unable to leave my bedroom for hours, in fear that he’d be waiting for me, ready to kill me. His face sometimes still haunts me, that lack of any emotion just ready to kill. Sometimes I wake out of a deep sleep, panting, fighting my way out of a choke hold that isn’t currently happening. Sometimes tears well up in my eyes unexpectedly reminding me of how scared I was and still am that he will come for me again. Sometimes I feel like I can’t function, like I don’t want to be out in the world. I have this crippling fear that I work through because I have to now. I have to be able to get up each day to tell him that I did survive, that what you did doesn’t control me, that you did not kill me, that you will not be my story.

True monsters exist out in the world. Philip Chism is a monster, a murderer. I have no doubt that his intention was to beat me into submission and eventually kill me. My recommendation to the courts is that he remain in prison for the rest of his life, locked away without the means to hurt another person. Time will not erase or fix what he has done or how he has affected my life. I have to constantly live with these memories. I accept that. We should not accept nor allow him to hurt anyone else. Please do not give him that opportunity ever again.