"Sources said the detective - who had just a year to go before retirement - was pronounced dead at Jamaica Hospital, and the sergeant is expected to survive", NY1 reported.
Arwindern Singh, who lives across the street from the store, said he heard about 20 shots go off and thought they were firecrackers.
An NYPD detective has died after being shot while responding to a robbery in progress at a cellphone store in Queens, and a second detective is injured after also being shot, officials say.
"Tonight highlights the incredibly courageous actions NYPD members perform each day in the name of fighting crime and keeping people safe in every neighborhood".
Officers recovered an imitation firearm at the scene, believed to be what the suspect used in the robbery. The officer was killed in what appears to be "an absolute tragic case of friendly fire", NYPD Commissioner James O'Neill said in a press conference late Tuesday.
O'Neill noted that Simonsen was a married father of two and that his wife and mother had been in the hospital at the time of his death.
Giving a more detailed rundown of Tuesday's incident, NYPD Deputy Chief Kevin Maloney said a witness first called 911 at 6:09 p.m. and reported seeing suspect Christopher Ransom putting on a mask and entering the T-Mobile store in Richmond Hill.
Sen. Chuck Schumer said, "We are forever indebted to the courageous NYPD detective who was killed in Queens tonight and the sergeant who was wounded".
'Make no mistake about it, friendly fire aside, it is because of the actions of the suspect that Detective Simonsen is dead, ' the commissioner said as he choked back tears.
As for the weapon he pointed at officers, police say it was a fake gun.
Mayor Bill de Blasio and O'Neill met with Gorman at the hospital. It's the second time a police officer has been shot in the city in the past three months, AP points out. "He didn't have to be at work tonight", Palladino said. Brian Simonsen of the 102nd Precinct's detective squad.
"We miss him, we're going to miss him". Then the cops came out and put one guy in an ambulance'. "That bravery and that resolve is something that we all need to understand".
Gov. Andrew Cuomo has directed flags on all state government buildings to fly at half staff in honor of Simonsen.
"He was the kind of fellow who led by example", Palladino said.
Brian Simonsen is the first NY police officer to die in the line of duty since July 2017.
Officer Miosotis Familia, 48, was writing in her notebook when ex-convict Alexander Bonds strode up and shot her through a window.
In December, an officer on Staten Island was hit by friendly fire as officers responded to a domestic dispute call.