The fatal shooting of an airline passenger by a federal air marshal raised questions about the use of lethal force by federal law enforcement officers in the event of a bomb threat on an aircraft. Following a background report on the incident, a security analyst explains the training process of air marshals.

MARGARET WARNER: The fatal shooting aboard American Airlines Flight 924 in Miami marked the first time federal air marshals have shot a passenger since the Sept. 11 attacks.

Forty-four-year-old Rigoberto Alpizar, an American citizen, was on the flight bound for Orlando. Before takeoff, passengers said, an agitated Alpizar pushed his way to the front of the plane with his wife behind him.

WITNESS: I heard her say, "He's bipolar, he doesn't have his medicine." I heard the shots. She screamed, "My husband, my husband," and they detained her; they would not let her go.

MARGARET WARNER: Authorities said when Alpizar was confronted by two air marshals, he suggested he had a bomb in his backpack, ran into the jet way, refused an order to hit the ground and appeared to reach into his bag. At that point, they shot him.

JAMES BAUER, Federal Air Marshal Service: At some point, he uttered threatening words that included a sentence to the effect that he had bomb.

There were federal air marshals on board the aircraft. They came out of cover confronted him and he remained non compliant with instructions.

As he was attempting to evade them, his actions caused the FAM'S to fire shots and in fact he is deceased.

MARGARET WARNER: FAM is shorthand for Federal Air Marshal.

There was no bomb found, and authorities say there's no evidence Alpizar was a terrorist.

The number of air marshals flying undercover on U.S. flights has grown dramatically since the roughly 30 working at the time of 9/11. The actual number is classified, but reported to be around 4,000. The two marshals involved in yesterday's incident have been put on paid leave pending an investigation.

MARGARET WARNER: A Department of Homeland Security official said yesterday that the air marshals had acted "consistent with their training." And that's our focus tonight. What is their training, especially when it comes to the use of deadly force?

For that, we turn to Charles Slepian, a security analyst and founder of the Foreseeable Risk Analysis Center. He's a former security consultant for TWA Airlines and now provides training for the New York City Police Department.

And Mr. Slepian, welcome. Thank you for being with us.

CHARLES SLEPIAN: Thank you for inviting me.

MARGARET WARNER: Tell us, what are the ground rules, under what circumstances are air marshals trained and authorized to use lethal force?

CHARLES SLEPIAN: An air marshal has to make a very quick decision about using lethal force. And so he is confronted with the question, is lethal force going to be used by the subject that he is about to arrest, and if he feels that lethal force is about to be used, then he will use all the force necessary to effect his arrest or terminate the illegal conduct.

In the case of what happened yesterday, we are talking about a situation where there is a threat that a bomb is about to be detonated, you have a very, very short span of time to make a decision.

And they made their decision quickly that lethal force was going to be used. And they used it first.

MARGARET WARNER: And we should say that, of course, the full facts haven't been entirely established. But that is certainly the report from federal authorities -- that he threatened to use a bomb.

Now are there circumstances in which they're trained or encouraged to use less than lethal force, or is that really just not practical when faced with the kind of split second decision you are talking about?

CHARLES SLEPIAN: Well, when the issue is a bomb, there probably is not going to be an alternative to the use of lethal force. But as a general rule in training police officers with regard to the use of force, you use the amount of force which is minimally necessary to accomplish your arrest, and no more. That becomes very subjective. And different people can look at it differently.

But you are never to use more force than is necessary to accomplish your end, which is either to accomplish the arrest or to terminate the conduct.

MARGARET WARNER: Now if a marshal, and we'll just talk in the abstract here, thought that a suspect had a bomb, would it be impractical to either try to tackle him to the ground or try to shoot to wound rather than to kill? Why would those not be options?

CHARLES SLEPIAN: Well, let me take the second option first. It's very, very difficult to place a gunshot exactly where you want it. And what wounds one person doesn't always wound the next. So if you are going to shoot, you shoot to kill.

Now with regard to tackling, that would be probably totally out of the question because it is a split second in time to detonate a bomb.

MARGARET WARNER: And if the person, in fact, had a bomb that could even be maybe counterproductive?

CHARLES SLEPIAN: Well, absolutely, it could be counterproductive if he did have a bomb because that might force him to do something that he didn't intend to do.

But what you want to do is give him every opportunity within the timeframe available to you to make a decision to comply with your demand, and if he doesn't comply, then you have to use the force necessary to force that compliance.

MARGARET WARNER: And one other alternative that's been discussed are these taser stun guns. Would something like that -- and I know air marshals don't carry them -- would they have worked in a situation like that?

CHARLES SLEPIAN: Probably not likely. You know, we are constantly made aware of the fact that a taser was used three, four or five times to subdue an individual. They are not entirely reliable. It depends on the distance from the subject, it depends on the size of the subject; and it depends on the battery charge of the stun gun.

We're talking about something that requires an immediate response. And so in the case of an explosive, you really want to use your firearm, use it accurately and for it to have the effect necessary to terminate that threat.

MARGARET WARNER: And is it true, I read today, that in fact federal air marshals to qualify have to meet the highest standard of any federal law enforcement official in terms of handgun accuracy, accuracy in shooting with a handgun, is that true?

CHARLES SLEPIAN: Well, the service claims to maintain that level. I haven't gone through it but I believe that that is probably the case, and partly because the people who don't meet the standards of the Federal Air Marshal Service are generally individuals who have failed with regard to the use of their handgun.

It's a very, very rigorous training program, with tremendous demands as you can imagine, given the confined space of an airplane and the number of people who are packed together. You need to be right all the time.

MARGARET WARNER: Now, as we reported and as everyone who has watched this knows, there are some passengers who say that his wife said he was suffering from what we used to call manic depression or bipolar.

Are air marshals trained in psychological evaluation, in making a determination whether someone is simply either an unruly or perhaps mentally unstable passenger, versus a real security threat?

CHARLES SLEPIAN: Well, all law enforcement personnel receive some training in a psychological reaction. But in an instance where you are dealing with someone who claims to have a bomb, you have no time for a psychological evaluation. You have to take on face value that what the individual said is so. And you must act accordingly. You don't have the luxury of time to analyze them.

MARGARET WARNER: And what kind of background do air marshals usually come from? I mean, we ramped up so quickly from 9/11 to today, where do they find all these mostly men, I guess, though there are some women?

CHARLES SLEPIAN: Well, most of them have been recruited from other services, other federal services. So you find a lot of former immigration police officers; you find customs agents; you find border patrol people who have accepted positions with the Air Marshal Service. And they have recruited beyond that as well.

There are people with military backgrounds. For the most part these are people who have experience in handling firearms and know how to use them appropriately.

MARGARET WARNER: And briefly, then, what else is added? What is the most important other thing that they learn in their training?

CHARLES SLEPIAN: They learn to be very decisive and one of the techniques that they use is to observe a situation, to orient themselves within that situation, to make their decision and to act without hesitation.

They really must act very, very quickly, and very, very effectively. And that training is drilled over and over again. They get it at their academy. And they get it when they are assigned to their regions around the country. So training is a continuous process for them.

MARGARET WARNER: Charles Slepian, thanks so much for being with us.

CHARLES SLEPIAN: Thank you.