The gunman who ambushed two New York City police officers as they sat in their car told two passers-by to "watch what I'm going to do."
Chief of Detectives Robert Boyce said Ismaaiyl Brinsley, 28, talked to people on the street just before the shooting.
The new details about the killer of officers Rafael Ramos, 40, and Wenjian Liu, 32, emerged as Boyce briefed the press Sunday afternoon, 24 hours after the events began on a street in the Bedford-Stuyvesant section of Brooklyn.
Brinsley shot his ex-girlfriend in her Baltimore area apartment early that morning, before presumably taking a bus to New York. The 29-year-old woman identified Brinsley as her attacker, Boyce said. She is expected to survive her injuries.
Brinsley shot himself to death on a subway platform as officers closed in on him.
As a result of the devastating attack, the NYPD ordered its forces to take extra precautions while on patrol.
Foot-patrol officers were ordered to work in pairs and detectives in teams of three, reports The New York Times. The department also pulled auxiliary police officers — unarmed volunteers — off patrol.
Despite theories that the shooting of the police officers was gang-related or that Brinsley, whose family is Muslim, had become radicalized, Boyce said the investigation has found no evidence of either.
Brinsley, a Brooklyn native, had at least 19 prior arrests — 15 in Georgia, 4 in Ohio — between 2004 and 2013. They were for a variety of charges ranging from misdemeanor assault and shoplifting to grand larceny and gun possession.
He served a two-year prison term in Georgia for criminal possession of a weapon and did several stints in local Georgia jails.
He was estranged from his family, Boyce said, adding that his mother said he had a troubled childhood and that she was afraid of him.
Brinsley's Instagram account contained rants against the government and police, as well as postings of how he was disappointed in his own life, Boyce said. He mentioned the Michael Brown and Eric Garner deaths, and said in his Instagram account that he planned to kill police.
Boyce defended his department against criticism that a fax from the Baltimore police warning of Brinsley's intention went unheeded. He said the departments already had been in contact with each other before the fax was sent, and that it arrived just one minute before the two officers were shot.
"At this point it would be unfair to categorize anybody as being slow," Boyce said. "We were still figuring this thing out at the time."
There were 10 eyewitnesses to the shooting of the officers, and Boyce singled out two "particularly courageous" Consolidated Edison workers who, after witnessing the shooting, chased Brinsley in their truck, shouting to officers on the street who then engaged Brinsley in chase.
There were also 10 eyewitnesses to Brinsley's suicide on the subway platform, Boyce said.
Brinsley's rampage began at 5:30 a.m. Saturday when he used a key he wasn't supposed to have to enter his ex-girlfriend's Owings Mills, Maryland, apartment. An argument ensued and he shot her, fleeing with her iPhone.
He called the woman's mother several times, expressing regret, and indicating to her where he was headed. She tipped off police to Brinsley's intentions.
The Associated Press contributed to this report.