A 911 dispatch brought Detective Brian Simonsen and Sergeant Matthew Gorman to a cellphone store in Richmond Hill, Queens on February 12.

"Gunpoint robber at T-Mobile. He's got a duffle bag. He's about 5'10", medium build. Saw him take two employees to the back," said an NYPD 911 dispatcher.

Police say the suspect, Christopher Ransom, raised a gun and made motions as if he were shooting.

"With the suspect advancing toward them, the officers discharged their weapons and retreated out of the store. That was when Detective Simonsen was shot," said Police Commissioner James O’Neill.

That incident, which resulted in the friendly fire death of Simonsen, highlights a troubling crime trend: robbers targeting city cellphone stores.

"A lot of times, they come in masked up or hoods, disguising themselves. Until you get somebody a person of interest, you kind of have to be out there and digging and digging and digging through video and everything else," said Andrew Boss, supervisory special agent with the Bureau of Alcohol, Tobacco and Firearms. 

Boss leads their Joint Robbery Task Force wi​th the NYPD. 

"They're coming in usually one, two, three, four individuals guns drawn, and they sometimes type tie up the clerks, certainly threat of force, get them into the back, get to the safe if there's a safe and take out as many cellphones as they can," said Boss.

"It used to be cellphone stores were robbed just for the money. Maybe they would take one or two phones. Now, they're going in and they're taking 20, 30, 40 phones at a time. And that's because of the aftermarket value," said Lt. Keith Smith, commanding fficer of the NYPD/ATF Joint Robbery Task Force.

About 400 phones seized from suspects are kept in a vault at the unit's Bronx headquarters.

"A lot of these phones are going overseas, which is definitely a problem. You know, every single phone that stolen, we do an Apple subpoena, we call it. We find out who actually is using the phone currently, and a lot of these phones are ending up in Africa and Eastern Europe," said Smith.

Those who purchase stolen phones aren't off the hook.

"If you go out and buy a phone for, $4,000 phone for $400 and you don't know it's stolen, you may find the police knocking at your door, or you may be walking down the street and we're tracking that phone and we're going to pull you in," said Smith.

Last year, there were 71 robberies of city cellphone stores. That number is declining this year, police say, because of the work of the Joint Robbery Task Force.