A massive gas explosion that tore through a vacant Atlanta apartment unit late Tuesday was caused by someone trying to steal copper, according to Atlanta Police.

The blast, which happened just after 10 p.m. at the Northside Plaza Apartments on Markham Street - less than half a mile from Mercedes-Benz Stadium - left part of the building shredded and sent debris flying across the courtyard.

"I've never seen anything like this before"

Resident Sincere Stanley told CBS Atlanta he had just returned home from work when he saw the destruction.

"It was crazy. That's all I can say. It was real, real crazy. I've never seen anything like this before."

Emergency officials say the explosion happened hours after two separate 911 calls came in from nearby businesses—one around noon and another around 2 p.m.—both reporting a strong smell of gas.

Investigators: Fire set inside vacant unit ignited the blast

Police say investigators spent hours picking through the rubble and determined someone broke into the vacant unit to steal copper. During the theft attempt, the person lit a fire, which ignited built-up gas and caused the explosion.

A person of interest was badly burned in the blast and is now in the hospital, authorities confirmed.

Residents shaken - even those who didn't hear it

Some residents didn't realize anything had happened until after the fact.

Montrez McKiver, who lives a few buildings away, said he slept through the explosion.

"I live on the other side and I have a sound system in my house… when I come home I'm in my own world."

He said friends called repeatedly to wake him up.

"I woke up around 12 o'clock and saw blue lights and white lights."

Building was already cleared for redevelopment

The unit that exploded had already been vacated as part of an ongoing redevelopment plan for the complex. Nineteen other units remain occupied, but management told CBS Atlanta those homes were not damaged and residents were not displaced.

The property management company says it is fully cooperating with investigators.

Authorities have not released the identity of the injured person, and the investigation remains ongoing.