7 On Your Side Investigates: The chaos of friendly fire shootings

NEW YORK CITY (WABC) -- The fatal shooting of an NYPD detective during the response to an armed robbery is putting a spotlight on friendly incidents.

Detective Brian Simonsen was caught in the crossfire as seven officers fired 42 rounds at a suspect said to be charging at them with a fake gun inside a Queens T-Mobile store Tuesday night.

He tragically died on the way to the hospital, while his partner suffered a gunshot wound to the thigh.

It is as intense and as dangerous a situation as any for police -- an armed robbery with hostages.

"Once again, T-Mobile, 1206 gun point robbery," police transmissions read. "The perp took two employees to the back of the store."

In a matter of minutes, confusion, fear, and adrenaline accelerate as police from the 102nd Precinct respond, including Simonsen and his partner, Sergeant Matthew Gorman, who were in the area investigating an unrelated matter.

Within seconds, police say the suspect charged out of the back of the store pointing that fake weapon at the officers as they retreated.

"When perp gets to front of the store, shots are fired," NYPD Deputy Chief Kevin Maloney said. "Seven members of service discharge 42 rounds during the incident."

One of those rounds hit Detective Simonsen, who becomes the sixth NYPD officer to be killed in friendly fire in the last 50 years.

"He's one of the best detectives on the job," retired NYPD Chief Robert Boyce said.

Related: Who is NYPD Detective Brian Simonsen?

We spoke to the recently retired chief of department about how friendly fire haunts every dangerous police response.

"You think you're being fired on, because you're hearing rounds coming," Boyce said. "You're not clear where it was, so this is the fog of war here. You're really not clear as to what's going on."

Friendly fire deaths of NYPD officers are extremely rare. The last one occurred nearly 10 years ago, when Officer Omar Edwards was killed by a fellow officer who thought he was an armed criminal.

Boyce said this most recent incident was not a case of mistaken identity, but that the police response will be thoroughly reviewed.

"So post-investigation into this matter, there will be a tactical piece that is looked at see what could have been done differently," he said. "But it is difficult to say they did something they shouldn't have done, because I don't think they did. I think it's just the circumstances."

It is also unclear whether Detective Simonsen would have survived had he been wearing his bullet-proof vest. He was struck in the chest.

"It is not uncommon for a detective not to wear his vest," Boyce said. "We stress it. We hope they do. But again, they're responding because they've done this time and time again. So you don't even think, 'Do I have my vest on?' You just go."

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