Gathering as much intelligence as possible and securing the location are the top priorities for law enforcement officials arriving at the scene of a hostage situation like the one today following the Binghamton, N.Y., shooting that left at least 13 people dead.
Brad Garrett, a former FBI agent and ABC News consultant, said authorities must try to make contact with the suspect, though the gunman in the Binghamton attack reportedly took his own life.
"You have to develop some sort of communication with the shooter, and that can be difficult, and he may not want to talk to you," said Garrett.
A senior law enforcement official told ABC News that 13 people were shot dead and another 26 were left wounded in the shooting rampage inside an upstate New York civic association building that caters to immigrants. Others were believed to be held inside the building as hostages.
"The biggest problem in this sort of situation is you don't know for sure that you only have one shooter, and you don't know exactly where he is," said Garrett.
Phones known as "throw phones" are often used to establish a connection with a shooter in a hostage situation, Garrett said, and provide a secure line for the suspect to call out to authorities. Ensuring that the shooter does not get more upset, he said, is imperative in a hostage situation.
"What you have to do when you're talking to a hostage keeper is realize that he's going to be in an acute, agitated state," said Garrett. "You have to get them on the phone and let them talk to you.
"Get them to engage with you, let him talk to you and basically have to agree with him and say I understand why you're doing it," he said. "You're going to have to get him to believe that you're on his side."
According to multiple state law enforcement officials, the gunman entered the one-story American Civic Association in downtown Binghamton about 10 a.m. today and began a shooting spree.
Authorities who can enter the building during a hostage situation must also treat everyone inside as a potential threat, according to Garrett
"They have to clear that building -- every room, every closet, every bathroom," Garrett said. "They're going to have to treat each person as a bad guy even though they may not think he or she is, because you have secure everything."
"You just still won't know what you have until hours later," Garrett said.
Dr. Harold Bursztajn, a hostage negotiation consultant and associate clinical professor of psychiatry at Harvard University, said it's important for anyone communicating with a hostage taker to remain calm.
"Probably the hardest part [as a negotiator] is that you have to be nonjudgmental," Bursztajn said. "This is hard when every fiber in your body wants to judge this person."
"Much of the technique is a matter of attitude," he said. "You have to be very self-reflective so that the attitude you have when you approach him is a nonjudgmental, calm attitude."
Getting the Shooter Out Alive
One of the goals of negotiators, particularly when there have already been killings, is to prevent the shooter from taking his or her own life. Garrett said one method commonly used by hostage negotiators is to talk about something that might be missed if the shooter is considering suicide.
"You have to get to the heart, find out if anything has any meaning to him," he said. "Let's say he has a kid who he wants to see -- maybe he wants to stay alive for him."
But Garrett admits that often, as in the Binghamton situation, negotiators are fighting a losing battle.
"It's a huge longshot in these types of situations that the shooter will come out alive," he said.
Garrett said negotiators can use the conversation to steer the shooter toward a window and possibly become a target by snipers, especially in an instance where a peaceful ending looks unlikely.
"The communication and the negotiation many times in situations like this is just a time buyer," he said. "You're buying time when he's not shooting more people so that you can get more information and boost your intelligence."
But once a killer has taken the lives of others and police close in, suicide is not an unusual outcome.
"When a person gets to that point where they go into a situation like the one in Binghamton and act that irrationally, they turn around and realize their life is over and decide to kill themselves," said Jack Cloonan, a former hostage negotiator with the FBI and an ABC News consultant.
Cloonan said that not knowing whether a shooter is under the influence of any drugs or prescription medication can also make the situation hard to navigate.
"It's a highly charged environment," said Cloonan. "Do we know if the person is doped up? Self-medicated? You just never know."
Shooting Location Can Be Revealing
Taking into consideration where a shooting like the one in Binghamton occurred, said Cloonan, can also help negotiators.
"If this is a place where people go in to talk about citizenship, and it attracts immigrants and someone goes in and does this, then the first thing that comes to a negotiator's mind is whether this is a hate crime or an anti-immigrant crime," he said.
Shooters often want to talk to negotiators about exactly why they did what they did, Cloonan said.
"More times than not the person on the other hand is going to tell you what happened," said Cloonan. "They are going to want to explain their thinking because they're proud of what they've done. They want to be recognized."
"They will explain in some detail what their grievances are," he said. "You can elicit a lot of information by simply saying, 'What happened? People are not shy about talking."
Cloonan said hostages who have escaped the scene can be very useful to hostage negotiators.
"The hostages themselves and witnesses are absolutely critical," he said. "One thing you want to know and what these people can sometimes tell you is if the shooter is acting alone."
While the job of a hostage negotiator is over once the shooter has been apprehended and the scene is secured, it's often a long road to recovery in terms of the mental toll a violent shooting takes on an investigator.
"The loss of innocent life when you're in the middle of negotiation is very hard to process," he said. "You do need to be decompressed after handling these situations."
Additional reporting from ABC News' Dan Childs.