PHILADELPHIA (WPVI) -- Questions are swirling in Philadelphia and around the country after a Black man was shot and killed by police officers earlier this week.
On Wednesday, a law enforcement expert weighed in on the tactics used by officers and the need to train more officers to use Tasers during tense encounters.
The video gripped the city. It shows roughly 30 seconds of police confronting Walter Wallace Jr. before fatally shooting him.
The scene is chaotic as both family members and officers scream.
RAW VIDEO: Video shows officers yelling 'put the knife down' before fatal shooting
"This is not a call police officers have typically been trained to handle or are equipped to handle," said law enforcement expert and ABC News contributor, John Cohen.
Cohen said the critical question in the aftermath is not whether lethal force was justified, but rather: did police do everything they could to minimize lethal force?
Cohen said de-escalation is paramount, especially when dealing with mentally disturbed people like Wallace.
"How the officers approach the individual and how they talk to the person in a calm voice, talking to that person from a position of cover, so if they act erratically that officer is in a position of safety."
What happened during the entire police response is currently under investigation.
Since Monday, calls for police to release body camera footage have been growing louder.
"The idea that a police officer can shoot someone in the hand to drop a knife or gun or shoot them in the leg, that's just not how police officers are trained and doing that may place the officer in jeopardy," Cohen said.
What sort of de-escalation training the officers had is unclear.
Cohen says more police departments across the country are now embedding mental health experts to respond to such situations to prevent those critical second officers where police have to make a deadly judgment.
"It's really hard for anyone outside of those officers to really understand what they are feeling at that time, whether they feel in jeopardy or whether they feel their life is being threatened," he said.
Many people have called for the use of a Taser in this incident.
Cohen said they could've been used, but the officers involved were not equipped with them.