By Catherine E. Shoichet
(CNN) — The day ended with two slain New York police officers. But it started, investigators say, when Ismaaiyl Brinsley slipped into his ex-girlfriend’s apartment using a key he wasn’t supposed to have.
A fight quickly erupted around 5:30 a.m. Saturday after Brinsley used that key to unlock the door of an apartment in the Baltimore suburb of Owings Mills, Maryland, New York Police Chief of Detectives Robert Boyce told reporters.
Just 20 minutes later, calls of a shot fired there came into 911.
Shaneka Nicole Thompson, a 29-year-old who’d known Brinsley for about a year and was once romantically involved with him, had been shot in the stomach with a 9mm semiautomatic handgun.
By the time police arrived, police said, Brinsley had fled — stealing Thompson’s cell phone and carrying it with him as he headed north on the highway.
Minutes later, he call her mother and apologized, telling her he’d shot Thompson “by accident and that he hopes she lives,” Boyce said.
She was critically wounded, police said, but is expected to survive.
It was one of Thompson’s friends, Baltimore County Police said, who alerted them Saturday afternoon to troubling Instagram posts the friend believed came from Brinsley.
“These posts included overt threats to kill police officers,” police said, and they appeared to be posted in Brooklyn, New York.
“I’m putting wings on pigs today…they take one of ours, let’s take two of theirs,” one Instagram post said.
Around 2:10 p.m., 40 minutes after speaking with the friend, Baltimore County Police said they called a New York Police Department precinct to warn them. Then they faxed a “wanted” poster with Brinsley’s picture.
“Suspect is armed with a 9mm handgun and has posted pictures on Instagram saying that he will shoot a police officer today,” a description on the flier says.
“PLEASE USE EXTREME CAUTION,” it says in large red letters. “THREATS ON POLICE,” it continues. “ARMED SUBJECT.”
But the message to be on alert apparently came too late.
While New York Police Department notifications about the warning were going out, Boyce said, Brinsley ambushed two officers in their patrol car, shooting them dead.
Lengthy criminal history
Long before Saturday’s shootings, Brinsley was no stranger to police.
He had an extensive criminal record, including at least 19 arrests, a 2-year prison term and several stints in Georgia jails, Boyce said.
Brinsley’s mother told detectives she hadn’t seen her son in a month. He “had a very troubled childhood,” “was often violent” and had tried to commit suicide, she told them, according to Boyce.
It wasn’t immediately clear, Boyce said, how Brinsley got the gun he used to shoot his ex-girlfriend and two police officers before turning the weapon on himself.
A man bought the handgun at a Georgia pawn shop in 1996, when Brinsley was just 9.
Detectives are working with the Bureau of Alcohol, Tobacco and Firearms, Boyce said, “to find out where (the gun) could have fallen into his hands.”
Detectives comb social media posts
On social media, Brinsley also had a history, posting numerous rants on Instagram, Boyce said. Detectives are investigating his past posts on Facebook and Instagram, and looking through his e-mails and phone records.
“What we’re seeing from this right now is anger against the government, anger at the police,” Boyce said.
Some posts mentioned Michael Brown and Eric Garner, whose killings by police have sparked protests across the country.
“I always wanted to be known for doing something right,” one of his last posts on social media said. “But my past is stalking me and my present is haunting me.”
Shortly before he shot the officers in New York, Boyce said, Brinsley spoke with two people and asked them three things.
“He asked for their gang affiliation,” Boyce said. “He asked them to follow him on Instagram. And then he says, ‘Watch what I’m going to do.’ ”
CNN’s Andy Rose, Shimon Prokupecz and Nick Valencia contributed to this report.
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