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."
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."