Police are continuing to search for information regarding the death of a Cambridge, Massachusetts teenager, according to the Middlesex County district attorney.
Investigators are looking to identify any witnesses to the incident and information concerning the identity of a person seen in the area on a bicycle.
The 15-year-old girl who died Monday after being assaulted on Sunday was a student at Cambridge Rindge & Latin School, according to school officials.
The teen's name was not released by school officials, but school personnel and grief counselors will be at the high school on Tuesday for students and staff who would like to talk.
"Our thoughts are with this young woman and her family," the school said in a Facebook post.
The school is in the midst of summer session and the young woman who died attended summer school.
"Everyone knew her... it's sad because she was just here a couple of days ago and now she's gone," classmate Francesca Rivera said. "She was always a happy girl, so to see that something like this would happen to her... why?"
Police responded to the intersection of Cambridge and Warren streets around 6:30 p.m. Sunday, where they found the victim, according to DA Marian Ryan.
One of the owners of Portugalia, a nearby restaurant, couldn't believe what she saw outside the front door after the attack.
"When we went outside, she had fallen and she was bleeding from her nose and her mouth and she was pretty listless," Maria Valente said. "She was unconscious and she needed help."
The girl was reportedly walking to a friend's house when she was shoved to the ground and hit her head, authorities said.
"My first reaction was to call 911," Valente said.
Medics and police responded quickly. The girl was taken to a local hospital in critical condition. Monday afternoon, she died from her injuries.
Another of Portugalia's owners says that even though customers also came running out of the restaurant to help the girl, none of the witnesses saw who assaulted her.
"So incredibly sad," Cambridge Mayor Marc McGovern said on Twitter. "My heart breaks for this young girl and her family."
"Heartbroken & angry that an early evening assault on a neighborhood street has taken the life of a 15yo female," added Vice Mayor Jan Devereux.
Officials said they initially believed the attack was a robbery, but they have since ruled that out. No arrests have been made.
The medical examiner's office is investigating the cause and manner of the girl's death.
Anybody with helpful information regarding the incident is urged to call police at (781) 897-6600.