LYNN — After being arraigned on Friday in Salem District Court, new details on 18-year old murder suspect Anthony DeMayo, who attacked 69-year-old Janet Swallow and stabbed her to death in her home on Amherst Street in Danvers, have emerged.

DeMayo is a Lynn resident and was finishing his senior year at Bishop Fenwick High School in Peabody. Multiple residents, including Ashley O’Brian, saw him carrying a knife while walking around Standard Street and making concerning motions with the weapon.

“He was kind of like taking the knife and gliding it across, and he was kind of just like practicing, it looked like, on them,” she said to CBS News Boston.

Officers observed, and then later identified DeMayo holding a reddish-brown stained knife. The district attorney’s office said that information led Lynn and state police to his home, where evidence was discovered through search warrant that led them to Amherst Street.

It was there that they did a well-being check and found Swallow dead in her bed.

Court documents reveal that DeMayo, who confessed to killing Swallow, told investigators “that he planned on committing this act for a long time, and wanted to kill someone for a long time.”

One resident, Rhonda Deparolesa, said that DeMayo even tried to break into their home prior to be arrested. Based on the investigation, he eventually entered into Swallow’s home by climbing through a window.

“I lock my doors, so I was like, ‘He’s trying to get in here.’ I saw his hand going on, and I’m like ‘No, no, no,” Deparolesa told CBS News Boston, adding: “All of a sudden, the police came, and he booked. He jumped over the fence, and they were yelling at him to stop.”

Essex District Attorney Paul Tucker noted the “randomness” of the attack and said that “there was no connection that we can find between the defendant and the victim.” DeMayo is currently being held without bail and will undergo additional mental evaluation at Bridgewater State Hospital.

Psychologist Dr. Joyce Perrotta noted concerns that DeMayo, whom she said presents depressive symptoms such as restricted affect, anhedonia, and suicidal ideation, could be impacted by an ability to rationally understand and make legal decisions.

DeMayo is scheduled to return to court next month.