ROSS TOWNSHIP (KDKA) — Police swarmed a shopping center in Ross Township following a police-involved shooting this afternoon.

Sources say the shooting happened outside the Big Lots store at Northland Plaza on McKnight Road in the North Hills.

The attorney general’s office said the incident occurred during a Bureau of Narcotics Investigations operation.

Allegheny County Police say narcotics officers were engaged in an undercover “buy-bust” operation in the parking lot.

Gunfire was exchanged. The target of the investigation sustained fatal gunshot wounds and was pronounced dead at the scene, according to police.

The man shot and killed was identified as Omari Thompson, 31.

(Photo Credit: Allegheny County Police)

The narcotics agent sustained multiple gunshot wounds during the exchange. The officer is reportedly alert and speaking to family members.

WATCH LIVE: Shooting At Shopping Center —

The Office of the Attorney General’s Office released this statement on the incident:

“The OAG officer involved in today’s shooting was shot twice and is in stable condition with no life-threatening injuries. This incident occurred during an operation by our Bureau of Narcotics Investigations. The Attorney General plans to travel to Allegheny County to visit with the officer and his family.”

“I heard four rapid gun shots, and then screaming,” Jason Kauffman told KDKA.

Sources say the suspect fired shots, hitting one of the agents. A second agent then returned fire, fatally wounding the suspect.

The undercover agent was taken to Allegheny General Hospital. He is in stable condition and his injuries are not believed to be life threatening.

WATCH: Pam Surano talks to people who were in Big Lots at the time of the shooting —

People shopping inside the store at the time of the shooting describe terrifying moments of chaos.

“It was chaos when I came out, literally chaos. Just police everywhere,” another eyewitness tells KDKA News.

The popular shopping plaza is home to a busy Big Lots store. Shoppers were shaken and scared, not knowing what was going on.

“I was in the store checking out, and I heard, ‘pop, pop, pop, pop, pop,’ and first I thought it was fireworks, and then one of the cashiers said, ‘That’s not fireworks, those are shots being fired.’ I immediately started turning around, running away,” witness Mary Schubring said.

The plaza approaching the West View/Millvale exit on McKnight Road is also home to schools: a Huntingdon Learning Center, a Tender Care, Cynthia School of Dance along with a NovaCare Rehabilitation Center and many other stores and business.

WATCH: Andy Sheehan reports live —

The busy plaza was full of shoppers, families and children on a beautiful afternoon.

As word spread of the shooting, shoppers inside the Big Lots ran through the store alerting others who ran to the back of the store to hide together.

“The group of us all ran into the warehouse, trying to find somewhere to hide, into the locker room. In the locker room we barricaded ourselves in,” Schubring said.

(Photo Credit: NewsChopper 2/KDKA)

From inside that warehouse, shoppers say they called 911 and when they came out, the reality of what had happened hit them: an officer-involved shooting feet away.

Rita Schindler was also inside the Big Lots when the shooting happened.

“It’s like, ‘what on earth is going on here?'” she asks.

“You hear too many of these things with police officers. It just breaks my heart.”

“I did see that they were doing CPR on a man, and it looked like they covered that gentleman up, that he had passed,” Schubring told KDKA News.

Those shoppers inside the Big Lots moved a refrigerator in front of the warehouse door, not knowing if someone was going to come in and open fire.

Everyone in the stores and schools locked the doors. They were not hurt, and KDKA was told the children fortunately didn’t know what was happening outside.

Police are expected to be on the scene for hours.

The FBI has offered assistance in the investigation.

Attorney General Josh Shapiro flew to Pittsburgh when he learned of the shooting and went immediately to the hospital.

He didn’t get to see the wounded agent, but he did meet and spend about an hour and a half with the agent’s family.

Shapiro told reporters outside Allegheny General Hospital, “While we were together, our agent was – is — in surgery. I expect, based on the information I received from the family, and from officials at the hospital, that he will make a full recovery.”

The wounded undercover agent was the only person wounded in the incident.

Thompson has a long list of run-ins with police, including drug charges.

Shapiro said, “In this case, understand, this individual [Thompson] decided to discharge his weapon into an agent of the Office of the Attorney General. He made the decision to make this a dangerous moment.”

Shapiro noted the shooting of one of his agency’s law enforcement officers took place as funeral services were concluding a few miles away for fallen Pittsburgh Police Officer Calvin Hall.

Shapiro said, “I hope everyone remembers and appreciates the dangers every single day that our undercover agents, Pittsburgh Police, police in this region, PA State Police, deal with every single day.”