Murder charges for Brothers for Life duo

Two members of Sydney's notorious Brothers for Life gang have been charged with gunning down a 50-year-old man in front of his twin daughters.

Joseph Antoun was shot after answering a knock at his front door in Strathfield on the evening of December 16.

His wife and six-year-old twin daughters were home when the known standover man was shot dead.

Detectives from Strike Force Kirkland investigated and on Tuesday arrested a 25-year-old man at Silverwater jail and charged him with murder.

His arrest follows that of a 24-year-old man in Parramatta on Thursday, also charged with murder.

Detectives say both men are members of the Blacktown chapter of Brothers for Life.

The 25-year-old is to appear in Burwood Local Court on Wednesday while the other man is due to appear in the same court on March 17.

State crime commander Mark Jenkins on Tuesday described the shooting as abominable.

"Any person that's been shot is absolutely a terrible incident to occur," he told reporters in Sydney on Tuesday.

"(For it to happen) in front of your children is absolutely horrible."

While not commenting directly on the possible motives behind the killing, Mr Jenkins acknowledged there had been a conflict between Mr Antoun and "others".

He said the murder highlighted the dangers of associating with criminals.

"If you involve yourself with criminals, then it's likely that you're going to get hurt," he said.

Mr Jenkins said a "large proportion" of the leadership of the Brothers for Life had been jailed following recent police investigations.

He also urged other members of the gang to speak to police about the criminal activities of their group before authorities "come knocking".

Police suspect other people were involved in the Antoun shooting, he added.