( CNN ) -- Philip Chism , a 15-year-old Massachusetts boy accused of raping and killing his math teacher in a high school bathroom , was arraigned Wednesday on attempted murder charges stemming from a separate attack on a female youth services clinician . Prosecutors laid out a narrative of what they said was `` the defendant 's intent to murder '' a female employee last month at the Dorchester Department of Youth Services facility where Chism is being held pending trial , the Suffolk County District Attorney 's Office said . A judge set bail at $ 250,000 and ordered Chism to not have contact with witnesses , including the victim . He is to appear in court September 19 and an automatic `` not a youthful offender '' plea was entered on his behalf . Prosecutor : Chism planned attack on youth counselor . Assistant District Attorney Mark Zanini said that on June 2 , Chism was in the facility 's main room , which is bordered by a low wall . A staff member was seated at a station behind the wall , able to look down into the room . Behind the staffer was a hallway used by staff . Zanini said Chism had refused to attend classes while in custody . Instead , Chism was instructed to sit and study at a table in the open room . Despite a rule that he sit at the table closest to his room , Chism allegedly sat at a table that provided him a view of the hallway behind the staffer , the statement said . At some point , the 29-year-old female victim , whom Chism had known for several months , walked down the hallway and entered a bathroom inside a staff locker room , according to the statement . Chism was `` confident the other staffer was distracted '' and kicked off his sandals , which would have made noise on the floor , before moving toward the hallway in a crouch that kept him out of the staffer 's view , Zanini said at the arraignment . Chism had a pencil in his hand and opened the door to the locker room , according to the statement . When the female clinician came out of the bathroom , Chism stared at her from about a foot away . He placed both his hands around her neck and began to choke her while pushing her back against the cinder block wall in the bathroom , according to the statement . The victim was unable to scream because Chism 's hands tightly gripped her throat , Zanini said . When she managed to get his right hand away from her neck , Chism punched her in the face , head and jaw , prosecutors said . She screamed as other staffers rushed to help her and restrain him , Zanini told the court . The victim suffered bruises to her face , jaw and head , along with a scratch on her back consistent with a tear in her shirt that appeared to be from the pencil Chism carried , according to the statement . Chism was charged with attempted murder by strangulation , assault with intent to murder , kidnapping and two counts of assault and battery with a dangerous weapon : a pencil and the cinder block wall . Chism 's attorney , Denise Regan , declined to comment . Chism is also accused of killing his algebra teacher , Colleen Ritzer . Chism , 14 at the time , used a box cutter he had taken to school to kill Ritzer , 24 , in October 2013 in a girls ' bathroom at Danvers High School , police and prosecutors said . Massachusetts teen admitted killing popular teacher , affidavit says . Chism pleaded not guilty to aggravated rape , robbery and murder charges in January . He is being tried as an adult . After Chism was reported missing by his mother on the evening of October 22 , police had his cellular phone company `` ping '' the location of his phone . The phone was found to be near the Hollywood Hits Theater , where investigators learned the teen had purchased a movie ticket and then left . A court affidavit said that when Chism was spotted by a police officer the next day , he was carrying a knife ; a search of his backpack turned up a bloodstained box cutter . Asked where the blood came from , Chism allegedly responded : `` The girl . '' Police said he was carrying credit cards and a driver 's license belonging to Ritzer , as well as a pair of women 's underwear . Police discovered Ritzer 's body in a wooded area near the school , covered with leaves and debris in an apparent attempt to conceal it , court papers said . Her throat was slit . Chism 's case for the alleged assault on the youth services worker is scheduled for a pretrial conference on September 19 , but his presence for that event has been waived , according to the statement . Caring , compassionate Massachusetts teacher was 'brilliant ray of light ' Police affidavit offers chilling details of teacher 's slaying . Teen pleads not guilty to rape , murder of high school math teacher .
Philip Chism , 15 , accused of attempted murder in assault on youth services worker . Comment: Prosecutors lay out narrative of what they said was `` the defendant 's intent to murder ''