NEW YORK (CBSNewYork) – The NYPD is mourning a detective killed in the line of duty Tuesday night in Queens.

Det. Brian Simonsen was shot in the chest around 6 p.m. while responding to a botched robbery near the corner of 120th Street and Atlantic Avenue in Richmond Hill.

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NYPD Detective Brian Simonsen (Credit: NYPD)

The area surrounding the T-Mobile store where the shooting happened was still closed off Wednesday evening. All day, officers and detectives have been in and out of the store.

Less than a minute after officers arrived Tuesday night, police say more than 40 shots were fired during the attempted robbery.

This afternoon, NYPD officials revealed new details about the shooting.

Watch: NYPD Officials Give Details On Det. Simonsen’s Death 

“Everyone knew Brian was the cop that you reached out to if there was a problem that needed to be handled,” said Chief of Department Terence Monahan. “The events of last night, and what Brian did, it just shows the sort of man he was. He didn’t have to be there.”

Simonsen, a union delegate for detectives at his precinct, had been at a meeting in that capacity earlier in the day and did not have to go to work. He went in anyway, and was in the station processing a robbery arrest when his supervisor, Sgt. Matt Gorman, approached him and the two went looking for a group involved in a robbery.

The two hopped in a police car to conduct surveillance.

At 6:09 p.m., a caller told 911 operators they saw someone put on a mask carrying a gun enter the T-Mobile store.

Simonsen and Gorman were around the corner conducting their surveillance on another case. They responded to the robbery call, along with six uniformed officers.

Christopher Ransom had allegedly taken the T-Mobile employees into the back of the store.

Gorman and two officers entered the store, and Ransom appeared from the back room, carrying what appeared to be a gun, Deputy Chief Kevin Maloney said.

“Upon arrival at the scene, the officers went to the store with other officers. And the perpetrator, Christopher Ransom, with a gun raised, simulating firing at the officers,” Monahan said.

The gun, police said, wound up being a toy.

“As they enter, the perpetrator comes from the back of the location, that office, and he presents himself with the firearm pointed in the direction of the officers. At that time, the officers exit the location, as the perpetrator continues running in their direction. When the perpetrator gets to the front of that store, shots are fired. We have a total of seven members of the service who discharge a total of 42 rounds during this incident. As a result of this incident, the two police officers are shot,” Maloney said.

Simonsen was struck once in the chest. He was not wearing a bulletproof vest – it’s department policy to wear one.

Fellow officers rushed the detective to Jamaica Hospital Medical Center in a police car, but he did not survive.

Gorman, 34, was shot in the leg. He was taken to the hospital by a passerby in a civilian vehicle and was listed in stable condition.

Sgt. Matthew Gorman (credit: NYPD)

“He’s still being treated. I can tell you, he’s not the least bit concerned about his own injury. He’s overcome by the emotion of losing his friend and his partner, Brian Simonsen, as are all the officers in the 102ng precinct that I visited today,” said Monahan. “I ask that every New Yorker keep Brian’s family and the members of 102nd precinct and every New York City cop in their prayers.”

Ransom, 27, was shot eight times. He was wielding an “imitation pistol,” Maloney said. He was rushed to New York-Presbyterian/Queens, where he was taken into custody and is expected to survive. He has prior convictions, including impersonating a police officer, Monahan said.

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Five of the officers were wearing bodycams that captured part of the shooting, Maloney said. There’s also surveillance footage of the incident from within the store, Maloney said. Simonsen fired twice, Gorman 11 times, and the other responding officers combined fired 29 times, according to Maloney. The shots were fired over a span of 11 seconds.

“Just understand: This happens in seconds. It goes from zero to 60. You’re investigating a possible crime and all of a sudden someone is charging at you, pointing what you to believe to be a firearm, simulating firing at you. It raises everything very quickly,” Monahan said.

Monahan called it “horrible.”

“This is the worst feeling that you could have. It’s the worst thing that we ever go through as a police department,” he said.

It’s not clear who fired the shot that struck Simonsen. Monahan said the blame belongs squarely on Ransom’s shoulders, adding the whole situation was caused by his actions.

The NYPD asked anyone with additional information about Ransom that might help their investigation to contact Crime Stoppers at 1-800-577-TIPS.

Police Commissioner James O’Neill called it a tragic case of friendly fire.

“This is an absolute tragedy, the worst outcome any police officer or family of a police officer could ever imagine,” he said late Tuesday night.

Watch: Mayor De Blasio & Commissioner O’Neill S On Det. Simonsen’s Death 

Mayor Bill de Blasio held a moment of silence for the 19-year veteran during a speech at PS 189 in Crown Heights.

“The bravery it takes to go into the unknown situation like that is extraordinary, and he gave his life for us,” he said Wednesday morning.

Black and purple bunting went up Wednesday outside the 102nd Precinct station house. Monahan was among those who stopped by to pay their respects.

CBS2’s Janelle Burrell spoke with community members who said Det. Simonsen will be remembered for the way he treated others.

“We’re talking about an officer who is literally the last of a dying breed, almost, especially in this neighborhood,” said Richmond Hill resident Polo Savinon.

Hailan Gamil said the 42-year-old was a regular at the deli where he works. A tribute has been set up outside the store.

“He used to come to this store almost every day to get water and soda,” he said. “Every time I saw him, he was smiling, talking to me like one of his friends.”

“I will miss this guy. I can’t believe I’m not going to see him anymore,” Gamil added.

“Make no mistake about it, friendly fire aside, it’s because of the actions of the suspect that Det. Simonsen is dead,” said O’Neill.

Gov. Andrew Cuomo ordered flags to be flown at half staff in honor of the fallen hero.

“I am deeply saddened by the shooting of NYPD Detective Brian Simonsen,” he said in a statement Wednesday. “This tragedy is a heartbreaking reminder of the risks the brave men and women in law enforcement face every day to keep us safe. On behalf of all New Yorkers, I offer my deepest sympathies to Detective Simonsen’s loved ones and fellow members of the NYPD.”

A police caravan drove Simonsen’s body from a Bronx hospital past an FDNY tribute to a funeral home in Mattituck, Suffolk County where officials lined the entrance in salute.

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Ransom is facing a slew of charges related to Tuesday’s tragedy, including second degree murder, aggravated manslaughter, and robbery.