Jacky Amazing Feng, 32, did not apply for bail in Campbelltown Local Court on Monday after being charged with three counts of domestic violence murder and one of attempted murder.
Police allege Feng killed his parents and one brother, and injured another brother before 1.30am on Sunday morning at Rosemeadow in southwest Sydney.
Outside court, a family friend of Feng and his surviving brother, said he didn't believe what had happened when he found out.
"I was a bit shell-shocked when I first heard," Jonathan Dalangin told Channel 7.
Mr Dalangin said he was hoping to see both Feng and his brother.
"I think he's going through mental things, he's a very troubled person," he said of the man accused of carrying out the attack.
Feng's father was found by police with serious head injuries along with the bodies of his mother and brother when officers arrived, police said.
NSW Police said Feng was arrested after arriving at the scene in a silver Subaru about an hour after the attack is alleged to have occurred.
Police suspect more than one type of weapon was used in the attack, possibly including a hammer, Superintendent Grant Healey said.
"We think that there's a bladed weapon involved, as well as some type of weapon that can create a blunt-force injury," he told reporters on Sunday.
Neighbour Linda Evans told AAP the family were "perfect neighbours" and didn't cause any trouble in her time living nearby.
The parents lived in the front house while the sons lived in a granny flat at the back of the property, Ms Evans said.
Feng's case will return to court on July 15.
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