Who was UnitedHealthcare CEO shooting suspect on the phone with moments before shooting?

A mysterious apparent phone call by the suspect wanted for the murder of UnitedHealthcare CEO Brian Thompson could provide a "real data point" for investigators to zero in on, law enforcement experts tell Fox News Digital. 

Video has emerged showing the unidentified gunman apparently holding a cell phone to his ear less than 15 minutes before he opened fire in Manhattan. Police later recovered a phone dropped in an alley that the shooter used to flee the scene. 

"If indeed he was on a phone call right then – his phone was live – you can dump the cell tower. You are going to need the search warrant for that and it’s a ton of data," former NYPD inspector and Fox News Contributor Paul Mauro told Fox News Digital. 

"You got the video – you have a pretty good place and time, so what that does [is that] it places that phone inside a particular cell grid, and you look in the data around when the call appears to have been made, and you look at the phone calls that were made there and by process of elimination you are going to get not only the phone number that was assigned to that phone, you are going to get who he called," Mauro added. "And now you got a real data point." 

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Former FBI investigator Bill Daly told Fox News Digital that law enforcement can go to a cellular carrier and through a subpoena "get additional detailed information not just about perhaps the one he called that we believe we see him speaking on the phone just prior to the incident, but also any other earlier calls that may have been placed."  

"We don’t know when he purchased the phone. That is also extremely important to understand – did he buy it here in New York? Is he from New York? Did he buy it some other place and bring it to New York? So there is a lot of information that can be derived from that one device without actually knowing what that verbal communication was," Daly added. 

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Former New York Homeland Security adviser Michael Balboni told Fox News Digital that information can be found based on the numbers inside the recovered phone. 

"You take a look at the numbers that he called. You start calling those numbers, you do a reverse directory, which they can do very easily, and then you just go and sit on the house if it’s a house, if it’s another mobile phone, who’s got the contract? And then you go talk to those folks," Balboni said. 

As of midday Friday, the suspect remains on the run.  

New York City Mayor Eric Adams told NY1 that "We’re on the right track" and "We’re going to bring this person to justice," according to the New York Times.