Another fatal police shooting has added ammunition to the national debate over whether police are too quick to use deadly force.
This time it happened on the campus of Georgia Tech in Atlanta, where Scout Schultz, 21, a fourth-year computer engineering major, was shot and killed Sunday after campus police responded to a 911 call about a suspicious person with a knife. The Georgia Bureau of Investigation later said Schultz made that 911 call.
The student's death has sparked new questions about controversial police encounters, which have seemingly escalated in recent years with such high-profile fatal shootings as those of Michael Brown in Ferguson, Missouri; Laquan McDonald in Chicago; and Philando Castile in suburban Minneapolis.
There are about 1,000 fatal shootings by police officers each year in the United States, according to a Bowling Green State University report from April.
Was lethal force necessary at Georgia Tech? How did the situation escalate so quickly? And how else can police defuse a potentially dangerous situation?
CNN interviewed several law enforcement experts to gain a better understanding of police officers' use of deadly force from their perspective. They said that every situation presents officers with a unique set of challenges. And every officer must make split-second decisions, under tremendous pressure, about whether or not to fire their weapon.
What are police thinking when they arrive at a scene?
When officers are dispatched, they may be provided information that is not totally accurate, said Chuck Canterbury, the national president of the Fraternal Order of Police.
"Once they arrive, the procedure is dictated by the person or persons at the scene. The response is not choreographed and officers have to adjust on the fly," Canterbury said.
In the Georgia Tech case, the 911 caller said the suspicious person was possibly intoxicated and was holding a knife and maybe a gun.
Maria Haberfeld, a professor of police science at John Jay College of Criminal Justice in New York, said that officers typically arrive at a scene in a "heightened state of mind ... they know they are going to face someone with a deadly weapon and there is fear."
No gun was found at the Georgia Tech scene, but Schultz was carrying a small knife inside a multipurpose tool, the GBI said. The student was barefoot, "disoriented" and in the middle of a "mental breakdown," family attorney L. Chris Stewart said.
But officers do not typically have the skills to diagnose a situation where mental health is an issue, Canterbury said.
"Where it takes months for a licensed physician to diagnose a specific mental illness, the officer does not have the ability to make a diagnosis," Canterbury said. "There is no standard playbook for what someone suffering from mental illness is liable to do."
How can police defuse a situation without shooting?
"Police officers have right to protect themselves and the public from undo harm," said Cedric Alexander, a nationally recognized policing expert and veteran police chief who was called in to review the Ferguson police department after the 2014 fatal shooting of Michael Brown. Alexander is now the Deputy Mayor of Rochester, New York.
But he and other experts agree there are specific steps law enforcement can take to tamp down tensions.
"The basic triad is -- to talk to people, keep a distance and bear less lethal weapons," said David Klinger, professor of criminology and criminal justice at the University of Missouri in St. Louis. Klinger is a nationally recognized policing expert and has done extensive research in officer-involved shootings.
"They try to establish dialogue, and try to figure out verbal ways to reduce the level of tension," Klinger said. "They try to figure out a way to calm down the person if he is in some sort of a psychological crisis."
At Georgia Tech, cellphone video shows officers repeatedly telling Shultz to put down the knife and not to move. In the video, an officer opens fire after Schultz takes a few steps forward.
"The action of the suspect dictates the action of the police officer," Canterbury said.
Officers couple verbal attempts to bring the situation under control with tactical positioning, experts say. For example, if a person with a baseball bat is only five feet away, police may have no choice but to use a weapon, Klinger said. But if the person stays further away and does not appear to have a gun police may try to come up with other alternatives.
"The one thing we know is the greater the distance, the lesser the threat," Klinger said.
Why do officers shoot to kill?
Scout Schultz was shot once in the heart, according to Lynne Schultz, the student's mother.
Officers are instructed to aim for the center mass of a person's chest because it is the target they are most certain to hit and is most likely to take the suspect down, said Alexander.
"The whole notion of shooting him in the leg, or shooting the knife out of someone's hand in a stressful situation, that's all television. That does not work in life," Alexander said. "Police are trained to shoot center mass."
If a suspect has a firearm, the officer will not aim at an arm or leg because they are more likely to miss and thus not stop the threat, agreed Klinger.
If a suspect does not appear to have a gun, officers might take "carriage" shots at the legs to neutralize him, Klinger said.
Why don't they use Tasers or other non-lethal weapons?
All officers are encouraged to use non-lethal means to subdue a suspect if they deem it feasible, experts say.
A stun gun, or Taser, is popular with some officers because it is a hand-held weapon that police can easily carry with them, Klinger said. Tasers, which have been around since the 1990s, shoot darts that create an electrical current, temporarily incapacitating a suspect's muscle functions.
"The officer can stand 15 feet away and can shoot and incapacitate someone," Klinger said.
But their safe use requires a great deal of training, and there are concerns that Tasers are occasionally misused or overused by officers.
They also are not always effective, said Canterbury.
"It's not like 'Star Trek' where you shoot a beam a thousand yards -- it's not accurate from a distance," FOP president said.
Lance Wallace, a spokesman for the Georgia Tech Police Department, told CNN their officers do not carry stun guns.
Klinger advocates the use of bean bag rounds, small fabric pillows filled with lead pellets that can be fired from a shotgun. They aren't typically lethal and can briefly immobilize a suspect. And they allow officers to maintain a safe distance between them and the subject, he said.
"When the person takes a step towards me, that person is still 30 feet away -- that's the advantage," Klinger said.
But Canterbury is less enthusiastic about their effectiveness.
"Ninety-eight percent of police officers on the street do not have bean bags," he said. "They are usually restricted for special operations units because they require a shotgun."
Do officers need more training?
A lawyer hired by Schultz's family told reporters that the Georgia Tech officer had "overreacted." The officer shot the student because they "either weren't trained or they lost patience," L. Chris Stewart said in a news conference Monday.
Professor Haberfield, who provides leadership training to multiple agencies including the NYPD, said she would like to see more training given to police officers beyond the standard 15-17 weeks. She cited the example of Finland, where officers are trained for three years.
Some police departments use "shoot, don't shoot" simulators that plunge officers into realistic scenarios to sharpen their decision-making about when to fire their weapons.
Canterbury agreed that there needs to be more police training. But he said most police departments are understaffed and can't afford to pull officers off the streets for training.
Besides, suspects can be unpredictable, he said.
"No training in the world will tell you what a person is going to do," Canterbury said. "There is nothing in our oath of office that says a police officer should be shot or wounded. Police officers have a right to go home to their family as much as citizens do."