UPDATED 07/25/12 9:24 p.m.

GARY, Ind. (CBS) — The Gary Fire Department says an apartment fire that killed a mother and her daughter early this morning was probably arson.

Gary Fire Department Investigator Steve Johnson says it appears the fire started in a hallway outside the apartment.

“It appears to be a deliberately set fire using some type of ignitable, flammable (agent),” he said.

A woman and a 14-year-old girl were killed overnight in a fire in this apartment building in Gary, Ind. (Credit: CBS)

Two people died in the fire: 33-year-old Bernice King and 14-year-old Angel Harris. The Lake County Coroner identifies them as mother and daughter.

Sources told CBS 2′s Mike Puccinelli that the people who set the fire were targeting King’s son. The Times of Northwest Indiana reported neighbors of the victims said an argument over an XBOX 360 might have prompted the setting of the fire.

Police were being tight-lipped about their homicide investigation, but did say there were shots fired in the building Tuesday night. However, they do not know if that is related to the fatal fire.

CBS 2′s Mike Parker reports relatives of the two victims said they were convinced someone threw a Molotov cocktail at the door of the apartment, but police would not confirm those claims.

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Police said they know who they are looking for, but wouldn’t release the suspects’ names.

Five others, including a firefighter, were hurt in the fire at the Lakeshore Dunes apartments at 5805 Kennedy Terrace.

Four of King’s surviving children were treated for smoke inhalation, and were expected to recover. The injured firefighter was treated and released at a local hospital.

Authorities say Gary Police have leads on the fire – and that it may have been set by someone who was upset over a video game he’d been sold by someone in the apartment.

Wednesday night, Gary police held roll call for the night shift outside the burned-out apartment.

Gary Mayor Karen Freeman-Wilson said the show of force was meant to send a message.

“We are working feverishly to make sure that any person that is responsible for these actions is held accountable, and that they understand that we will not tolerate this type of behavior in our community,” she said.

The victims’ friends and family have set aside a place of remembrance nearby.

“They were really good people. They were fun to get along with. Everybody was nice. People loved them,” family friend Brittany Buchanan said.

“All we’re doing is praying that whoever did this comes forward. Just come forward. You hurt a lot of people,” King’s sister, Michelle, said.

Upon arriving around 12:30 a.m. Wednesday, firefighters found the two-story brick building engulfed in smoke. Two people were trapped in the second-floor rear apartment, but by the time firefighters got to them, it was too late.

Witnesses say the mother and daughter were lifeless when they were rescued from the building and taken to the Methodist Hospitals’ Northlake Campus in Gary, where they were pronounced dead.

One neighbor said at first, he thought it was all a false alarm. But when he got out of bed, he realized he was seeing a real tragedy unfold.

“I just came back from Afghanistan, so I just jumped into action,” said the neighbor, Ronald Rochelle. “I started trying to open all the doors; knock on everyone’s doors to wake them up. Once I did that, I ran to the back, and I saw that the whole back was engulfed in flames, and they said there were children still inside, so we were trying to spray it with fire extinguishers. The department wasn’t here. Actually, the people who live here were the ones that got the children out.”