(TNS) — A shootout between a gunman and a police officer last week at a busy Harrisburg intersection in the middle of the day raised questions regarding the use of deadly force by law enforcement.

How are officers trained to react in such situations and what does the law allow?

It was at least the fourth shooting involving police officers in central Pa. in the past seven weeks in interactions with armed men. The first three shootings were fatal, but the gunman shot at Cameron and Maclay streets in Harrisburg last week survived his injuries and now is in jail.

A bystander recorded part of the incident on his cellphone and the video was shared on social media, allowing many people to see for themselves what transpired.

Police say the gunman in Harrisburg was wanted in connection with an earlier shooting on March 13, then pointed a gun at Harrisburg Cpl. Jeremy Crist, who had pulled over his vehicle about noon. The suspect fired at Crist and ran across the sprawling intersection surrounded by bystanders, including a panhandler. The officer fired back as bystanders ducked for cover and swerved their vehicles.

In all, a dozen shots were fired, including one that hit the suspect, later identified as Jacob Bucher III, 38, in his torso. Bucher was discharged from the hospital Saturday.

First things first: The county district attorney’s office is responsible for determining if a police officer firing their gun is justified or not. That is because the district attorney’s office is responsible for filing criminal charges — or deciding when not to.

Prosecutors’ rulings on officer-involved shootings do not review whether the officer followed training, policies or best practices; nor if the person shot can sue in civil court. The DA only reviews if a police officer can be charged with a crime.

To evaluate whether a shooting is legally justified or not, the district attorney relies on Section 508 of Title 18 of Pennsylvania’s statutes, which permits deadly force in some circumstances.

The law says police are permitted to use any force they believe to be necessary to arrest a suspect in Pennsylvania, or to prevent harm from coming to themselves or another person. Using deadly force, however, comes with an additional set of requirements.

Deadly force is defined as action “readily capable of causing death or serious bodily injury.” In most instances, that means the use of a firearm — but can also count as a baton strike to the head.

Under Pennsylvania law, police can use deadly force when they believe it is necessary to prevent death or serious bodily injury from occurring to themselves or others in Pennsylvania. The law is based on the officer’s “belief,” but that belief must be considered reasonable, and the U.S. Supreme Court has issued rulings that explain those parameters.

“We’re not lambs for slaughter,” said Raymond Marr, a career police officer who frequently testifies on the use of deadly force in court. He noted that a firearm being waved at a police officer satisfies the law’s requirements for the officer to use deadly force.

But police are also justified in shooting suspects to prevent them from resisting arrest or escaping in specific scenarios, too, according to Pennsylvania law.

Police can shoot a suspect if they believe shooting them is necessary to prevent them from escaping or resisting arrest if the suspect has committed or attempted to commit a “forcible felony.”

The use of deadly force has to be immediately after the incident, Marr said — having committed a forcible felony in the past does not give officers the legal right to shoot fleeing suspects days or weeks after a crime.

Forcible felonies are those involving actual or threatened serious bodily injury, not burglary or property crimes. That could extend from aggravated assaults to robberies, and some sex crimes too, where the criminal’s implicit threat of violence ensures compliance.

Under the law, police also may shoot suspects who are trying to escape and who possess a deadly weapon, if they believe shooting them is necessary to prevent them from escaping or resisting arrest.

Finally, police can shoot suspects who have indicated they will endanger human life or inflict serious bodily injury if they are not arrested without delay.

District Attorney Fran Chardo said when evaluating whether or not charges should be filed against a defendant, he cannot play “Monday morning quarterback.” He said he has to view the scenario from the perspective of the police at the moment, which is the way the laws have been interpreted by the Supreme Court.

“When we evaluate use of force, whether it is a police officer or any citizen, we evaluate it from the perspective of the person at the time,” Chardo said. “How a reasonable person would perceive events as they occur.”

An “objectively reasonable” standard established by the Supreme Court says the necessity for the use and level of force should be based on the officer’s evaluation of the situation considering “the totality of the circumstances.”

Marr referenced the National Institute of Justice has a use-of-force continuum, based on their research, which illustrates in general what officers are taught as far as how to respond to escalation by a suspect. He explained officers should take action based on one level higher than a suspect’s to maintain control.

If a suspect is attempting to intimidate an officer who is merely present on a scene, for example, the officer should escalate to verbal direction, according to the chart. If the suspect doesn’t comply, an officer should escalate to the next level, such as martial arts holds to exert control over them.

An officer who meets deadly force should respond with deadly force, according to Marr. When suspects reduce their resistance or force, then officers can do likewise, he said.

After reviewing a Facebook video of Harrisburg’s recent shooting, Marr noted that as soon as the suspect threw down his firearm, police switched from using deadly force to a stun gun, a lower level.

Chardo said his office is reviewing the incident and should reach a determination relatively quickly. He did not otherwise comment on the specifics of the incident.

Bucher recovered from his wounds at a hospital and now is in the Dauphin County Prison with no bail. Police charged him with attempted homicide, aggravated assault, discharging a firearm at a law enforcement officer, and illegal possession of a firearm. He remains behind bars with no bail.