Map: Deadly shooting
PHOENIX -- We're learning more about the teenage boy who pulled the trigger in a murder-suicide in northwest Phoenix on Friday.
Fifteen-year-old Matthew Bolton and 16-year-old Anastasia "Ana" Greer were both sophomores at Sandra Day O'Connor High School.
Police say the murder-suicide occurred at a home of Ana's friend near 43rd Avenue and Happy Valley Road.
Officers responded to a 911 call of a shooting around noon Friday and found two people dead in the home's front yard. Both victims had gunshot wounds.
Police say we may never know why Matthew shot and killed Ana, but it's now becoming clear that he had a history of violence and at least some people feared him.
"Ana was asked on Friday if she had any fears regarding Matthew and she said no, she didn't," said Sgt. Tommy Thompson with the Phoenix Police Department.
But police say that on Thursday Greer went into the school office and told the school resource officer that she was worried Matthew might beat up his other ex-girlfriend.
Matthew was not at school, but that girl and her parents were notified and they were concerned because the two teens reportedly had an abusive history.
"She had been a prior girlfriend of Matthew's," Thompson said. "He had grabbed her arm when she tried to walk away in the past and he hit her on her legs, causing bruising."
Police say on Friday, Ana told that girl that Matthew wanted to talk about things "civilly," but that girl refused. Coincidentally, there were reports of a gun on campus, but there was no firsthand information.
Still, the school investigated and just to be safe, school officials called Matthew's mom to verify his whereabouts since he was absent for the second day in a row.
Police say she verified that Matthew was home with his brother. That was at 10:45 a.m.
Friday was early dismissal. So at 11 a.m., Ana walked over to a friend's house. Police say Matthew called a friend for a ride to that same house.
"He said, 'I'll give you a ride but I need gas money.' Matthew told him that he had no money but said, 'I'll give you a computer.' He traded his computer for a ride," Thompson said.
The three teens hung out at the friend's house, until, for some unknown reason, the friend asked Ana and Matthew to leave.
The friend described Matthew as seeming fidgety.
"He asked him if he had a gun and he said he did not," Thompson said. "As Matthew walked out, and before Ana could leave, the young man asked Ana if she had any weapons or anything that she could use. She said no and he then handed her a folding knife."
Witnesses next report seeing Matthew chase Ana down the street, shooting her in the back before ultimately turning the gun on himself.
Police also know now that Matthew stole the gun from his older brother, who owned it legally. Detectives plan to comb through Matthew's computer but aren't optimistic that they will ever truly understand why he shot and killed Ana.