What is the protocol for an interaction between police and legal gun-carriers?

The funeral for Philando Castile, a black man killed by police last week in Falcon Heights, Minn., was held in Saint Paul today. Mourners bearing signs "Unite for Philando" lined the streets, as his casket made its way to the church, just over a week after Mr. Castile died in his car during a police stop.

Castile's shooting, which happened the same week as the fatal police shooting of a black man in Louisiana, sparked demonstrations and vigils across the nation as the public reacted to another death of a black American at the hands of an officer. But the official investigation, being conducted by the Minnesota Bureau of Criminal Apprehension, has reportedly come to revolve around the manner in which Castile alerted officers to the presence of a legal firearm in the vehicle and how officers reacted to that information.

This focus raises the question – in a state with legal concealed carry of firearms for permit holders, what is the correct protocol for a gun carrier in a situation involving law enforcement and how should law enforcement direct such situations?

An attorney for Officer Jeronimo Yanez, who shot Castile, has now said that there is more to the story than the initial reports that the shooting occurred in the midst of a traffic stop related to a broken tail light. One of the reasons that Mr. Yanez and his fellow officer pulled Castile over, he said, was that he looked like a "possible match" for an armed robbery. The attorney, ABC News reports, says that Yanez reacted when he saw Castile’s gun.

Officers, in general, are trained to be on high alert when they approach a vehicle, whether or not they have reason to believe a gun is present.

“Statistically one of the two most dangerous things that a police officer does is a traffic stop,” says James Pasco, executive director of the National Fraternal Order of Police, speaking in general terms and not about the Castile case specifically. This is because officers never know who they are walking up to, he explains.

“In a traffic stop you are always in a heightened state of awareness – or should be – and [the presence of] a firearm exacerbates that.”

Mr. Pasco says that in a situation where a civilian has a gun, the expectation is that the gun carrier will alert the officer that he or she has a weapon and the officer will then instruct that person on how to conduct him or herself. When there is “full disclosure and full compliance with the officer’s orders” there is no need for escalation to conflict, he says.

Training for these situations is not limited to law enforcement. In Minnesota, experts say that most firearm safety courses, which are required for a concealed carry permit, include instruction on what to do while carrying a weapon in a traffic stop or a situation with law enforcement.

Castile reportedly fulfilled his course requirement in May of 2015 and received his permit in June. The course that Castile attended includes such law enforcement encounter training, according to Dan Wellman, owner of the firearm safety training center that Castile attended with his sister, Allysza, ABC News reported.

And while Minnesota state law does not require permit holders to tell law enforcement about concealed weapons unless they ask, the specifications for what do to in a traffic stop appear to emphasize transparency early on in the interaction.

Communication is key to these situations, explains Pete Cheolis, owner and instructor at Mind Sight Firearms Training, a gun safety training company in Maple Grove, Minnesota, who includes a section on law enforcement interactions in his courses.

Mr. Cheolis recommends that concealed carriers alert the officer early on in the conversation to the presence of the gun in the car, usually after the officer asks for a driver’s paperwork. He emphasizes that this must be done with both hands on the wheel and in plain view.

“You always want to inform the officer before you move your hands: ‘hey just to let you know officer, I’m a current permit to carry holder and my firearm is on my right side or in my backpack,’” he says. From there, you “let the officer walk you through the stop.”

Michael Briggs, a firearms instructor with Minnesota Firearms Training, a private company in Anoka, agrees, saying he instructs his students to keep their hands firmly “at ten and two” on the wheel when stopped and to then: “be friendly, don’t lie, and when they ask for your ID, if your firearm is on your hip and your ID is in your back pocket, volunteer that information up and let them know, ‘I have a firearm on me what would you like me to do next?’”

Mr. Briggs says that if the firearm is in another part of car, out of reach, then it would be appropriate to give the officer the carrying permit while handing over the ID.

Briggs, whose company also provides post-certification training for law enforcement and permit applicants, says that he also incorporates a discussion that can be applied to both cops and non-cops about the difference between being afraid and being in danger into his courses: "You can be afraid of somebody or afraid of a situation and not be justified in using lethal force, and it's important that people understand that.”

So far the details of Castile’s interaction with the police have been largely based on statements by Castile’s girlfriend, Diamond Reynolds, who was in the car and broadcast the moments immediately following the shooting on Facebook Live.

She says that Castile alerted the officer that he was carrying a firearm while reaching into his back pocket, after having first had his hands in the air, the New York Times reports. Ms. Reynolds says the shots started just as she was yelling “But he’s licensed to carry.”

In Reynolds's broadcast, which began after the shots were fired, an officer is heard shouting: “I told him not to reach for it. I told him to get his hands up.”

Castile’s family and Gov. Mark Dayton of Minnesota have said that they believe the shooting was racially motivated. The investigation will examine whether the sequence of events results in culpability for the officer.