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BROOKLYN (PIX11) — The NYPD on Sunday painted a chilling portrait of cop killer Ismaaiyl Brinsley’s last day, detailing his murderous journey from Baltimore to Brooklyn on the fateful day that left two of New York’s finest dead by his hands.

NYPD Chief of Detectives Robert Boyce said Brinsley, after leaving his ex-girlfriend for dead in a shooting outside Baltimore Saturday morning, jumped on a Bolt bus headed for New York, all the while posting ominous messages on an Instagram account.

When he finally hit the streets of Bedford-Stuyvesant Saturday afternoon, he was hunting for cops to kill, and said moments before the fateful encounter that passersby should “watch what I’m going to do.”

He then pumped four shots into the squad car outside the Tompkins Houses where  Officer Wenjian Liu and Officer Rafael Ramos were having lunch while on an anti-crime patrol.

A warning message from police in Baltimore to watch out for Brinsley arrived between 1:30 and 2 p.m. and the shooting happened at 2:47 p.m.

Timeline of horror

Brinsley’s rampage started around 5:30 a.m. Saturday at his ex-girlfriend’s apartment in Maryland. Using a key he should not have had, Brinsley entered the woman’s home and confronted her, Boyce said.

The woman, who wanted nothing to do with him, put up a fight. She called her mother and then hung up the phone. Twenty minutes later, around 5:50 a.m., calls of a single shot fired were received by police.

Upon arrival to her home, the woman identified Brinsley as her shooter and told authorities he took her phone as well. Meanwhile, Brinsley made several calls to the woman’s mother.

He told her the shooting was an accident and said he hopes she survives. The calls helped police track the man.

Brinsley continued to New York City using a Bolt bus. He arrived around 10:50 a.m. and then discarded her phone at Barclays Center.

Before shooting Officers Ramos and Liu in Brooklyn, Brinsley made contact with two men, who police believe have no connection to the homicide. He asked them if they had any gang affiliations and told them to follow him on Instagram. Before parting ways, Brinsley told the men to watch what he was going to do.

Brinsley fired four shots at the unsuspecting officers, which was witnessed by two Con Edison workers who followed the man in their truck and notified police about the attack.

Police do not believe Brinsley is affiliated with any gangs. There are no tattoos indicating his affiliation with any group. His mother, who has not see him in a month, told police the man had a troubled past, but never expressed any radical behavior. She lives in Brooklyn.

She did, however, say he had a violent childhood and expressed fear of the 28-year-old man. Brinsley may have had an undiagnosed mental illness and might have been on medication later on in life.

Brinsley was born in Brooklyn and went to high school in New Jersey. Because of his troubled life, he often traveled back and forth to Georgia, which was listed as his residence.

Police said his Georgia address turned out being the home of his estranged sister, who had not seen him in two years.

Brinsley had a long criminal history and was in and out of jail in Georgia and Ohio for an assortment of crimes, including grand larceny. In August 2011, he served a two-year prison term in Georgia.

The man’s social media activity was filled with several anti-government and anti-police statements. There were also posts indicating his self-despair and his mother told police, Brinsley attempted to commit suicide in the past.

Investigators are still trying to account for 2 hours and 40 minutes of Brinsley’s route. They recovered two MetroCards from his possession.

They also identified 10 eyewitnesses and recovered five videos at the scene, including two before the shooting, two after the shooting and one in the subway. None of the videos depict homicide, Boyce said.

The killer was last seen wearing a green varsity jacket with a Red Indian logo. Police ask that anybody with information come forward.