Joshua Thompson, 20, was living in building one of a three-block unit complex on Bligh Street in mid-2021 when he began targeting a woman living in block three.

Documents tendered to Wollongong Local Court do not reveal the origin of the dispute, however Thompson admitted setting fire to the woman's building twice in the space of two months, in between leaving disturbing notes on her doorstep.

The court heard Thompson entered the stairwell of block three just after 1am on June 26 carrying two pillows, which he placed on the second storey landing.

He set fire to the pillows before fleeing, police said.

The blaze activated the building's smoke alarms, which woke a nearby resident, who managed to extinguish the fire using a bucket of water.

No one was harmed as a result of the incident, however police said several residents would have been trapped if the fire had managed to spread.

Meanwhile, the victim told police she found a handwritten note under her door five days later, in which Thompson called himself "Jayden Riot", told her where he lived and threatened to make her "go missing".

"You fat dumb dog, you (sic) going to get bashed that bad your family won't no (sic) who you are," he wrote.

"[I] swear dog, I'll get you on the street or I'll do one better, I'll smash your windows.

"I am going to make you go missing and by the way I live in the middle block next to you so u (sic) better call the cops to help you before it's too late."

The court heard Thompson left another note at the woman's door on July 4, claiming he'd been watching her ever move.

"I swear I [am] going to blow your house up with you in it you fat ugly mutt," he said.

"You're going to be up in flams (sic) soon, the fire in the stairwell the [other] night was for you dog."

The note was signed with a smiley face.

Court documents said Thompson and a second person were then captured on CCTV nine days later setting fire to a mattress in the stairwell of the woman's unit block in the early hours of the morning.

The building's sprinkler activated, eliciting an automatic call out from firefighters. The building sustained minor smoke and water damage but no one was injured.

Thompson was arrested in August and taken to Wollongong Police Station where he was charged with damaging property by fire with intent to injure another.

Thompson initially denied the allegations but has since pleaded guilty to the charge in court.

He will face Wollongong District Court on May 6 where a date will be set for his sentencing.

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