As security preparations intensify for Charlie Kirk’s memorial service in Arizona, a former NYPD detective and security consultant warns mourners to remain alert.

“Pull your face out of your phone, put it in your pocket. Pay attention,” Pat Brosnan urged. 

The memorial, set for this weekend at State Farm Stadium, is expected to draw an enormous crowd. Officials estimate that more than 100,000 people may gather in and around the venue, including attendees inside the 63,000-seat stadium and overflow areas outside.

“From the moment you arrive… have your eyes wide open… who’s to your right, who’s to your left, who’s behind you? What are they doing?” Brosnan told Fox News Digital. “Eyes in the backs and the sides of your head.”

Despite the full weight of federal and local security coordination, Brosnan was realistic about the limitations of modern threat detection.

“There are weapons that could get past even the most technologically efficient systems out there,” he said. “The reality is, [those weapons] could get in there.”

Which is why Brosnan says public vigilance is not optional — it’s essential.

More than just a technical or tactical issue, Brosnan says situational awareness is about shared responsibility.

“There could be someone near you who hears something, sees something — and they have to report it immediately, immediately, immediately,” he stressed. 

Kirk is survived by his wife, Erika Kirk, and their two young children. Erika, along with the president, vice president, and other dignitaries, is expected to speak at the upcoming service.

Kirk was fatally shot last week while addressing an event hosted by the Turning Point chapter at Utah Valley University in Orem, Utah.

The accused, 22-year-old Tyler Robinson, is currently in custody without bail and faces multiple charges, including murder.

Stepheny Price covers crime including missing persons, homicides and migrant crime. Story tips: stepheny.price@fox.com.