The son of an elderly man killed in a house fire has been charged with murder.

Edward “Ted” Grantham’s body was found after an “intense” fire caused the roof of his suburban home in Sydney‘s inner west, to collapse.

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The 80-year-old’s home on Irrara St in Croydon was reported ablaze about 4am on Wednesday.

Six trucks and almost two dozen firefighters attended the fire, entering the back of the property due to “intense” flames at the front of the single-storey red-brick house.

Part of the roof collapsed as firefighters were inside, forcing them to retreat, Fire and Rescue NSW said.

Grantham’s body was found inside the home after the blaze was extinguished.

Edward Grantham’s body was found after an ‘intense’ fire caused the roof of his suburban home to collapse. Credit: Facebook

A major search was then launched for Grantham’s 50-year-old son, Christopher Grantham.

He was “intercepted on a train at Woy Woy” about 7.40pm on Wednesday, Superintendent Christine McDonald said.

Police allege he had a machete, concealed in his pants, at the time.

He then allegedly “made his way on foot to a service station in Haberfield, where he threatened staff and demanded cigarettes”, McDonald said.

“We know at the time that he was in possession of a machete and he used that to threaten staff,” she said.

Christopher Grantham has been charged with murder, destroy or damage property with intent to endanger life — DV related, and armed robbery.

Police allege the 50-year-old deliberately lit the fire at the Croydon home.

Ted Grantham’s cause of death has yet to be determined and a postmortem examination has yet to be carried out.

Christopher Grantham was refused bail and will appear before Gosford Local Court on Thursday.

McDonald commended the actions of police on Wednesday in locating him.

“I am extremely proud of the efforts of the police,” she said.

“It took determination, investigative skill and teamwork to locate that man.

“I am very acutely aware that this could have been a lot worse, and him in possession of a machete terrifies me.

“To think what he could have done if we had not intercepted him in Woy Woy last night.”

The body was found inside after a fire engulfed the property. Credit: 7NEWS

The home on Irrara St at Croydon was reported ablaze about 4am on Wednesday. Credit: 7NEWS

Footage taken after the blaze was extinguished shows a large portion of the roof caved in and firefighters examining other parts of the extensively damaged home.

An elderly woman left the home about 1am and was not present for the fire, McDonald said on Wednesday.

She is understood to be another relative who lived at the home.

Police had not been called to the home before the fire started, McDonald said.

However, she confirmed Christopher Grantham was known to police.

McDonald said she had received an outpouring of messages about Ted Grantham.

“I am of the understanding that he was such a beautiful person, a great community man.,” she said.

“He was part of a church, he played the piano, he was a teacher.

“There are far and wide consequences to this investigation and my thoughts go out to not only the immediate family but the wider community because I know from the text messages that I’ve received that this has had a rippling effect throughout our entire community.

“This is such a tragic set of circumstances.”

— With AAP