An 18-year-old man arrested as part of a counterterrorism operation on Saturday changed for the better after attending the Al Furqan Islamic study centre in South Dandenong, the man’s father says.

Harun Causevic was one of the five men in the anti-terror raids who were allegedly involved in plotting an attack on police involving edged weapons in Melbourne during Anzac Day activities.

Sevdet Besim, 18, of Hallam, was also arrested and remanded in custody after being charged with conspiring to commit a terrorist act.

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One man will be charged with weapons offences and two others have been released without charge.

Police entered into Causevic’s home at 3:30am Saturday and stayed there for more than 12 hours, seizing a knife, phones and a USB from the accused man’s bedroom.

His father, Vehid Causevic, said the family was traumatised when police broke into their home in the early morning hours.

He said he had a gun held to his head and was forced to lie on the floor for 30 minutes.

Mr Causevic said police told him: “One more word I kill you. Doesn’t matter for your kids.”

“My wife she starts screaming. Police call ambulance to come and help her,” Mr Causevic said.

“I notice everything in the house is broken, the door, everything.”

Mr Causevic said his son was interviewed by the authorities after the police shooting of Abdul Numan Haidar in September 2014.

Haidar attended the Al Furqan Islamic study centre and Harun Causevic started going there in July 2014.

Mr Causevic said the changes in his son were all positive.

“Before he started to pray, Harun was in the house aggressive, he broke [things], like a child. But after when he started to pray he really changed behaviour, 100 per cent,” he said.

“Now he was very good, always. Never, never yells, never, never do bad in house.

“He’s always nice talking when I see him, but I (do) not see him very much.

“I told you I can’t see nothing that Harun would do bad.

“When he goes outside, I can’t tell you nothing because his life is one, my life is one.

“I can’t tell you nothing about what he’s doing with his friends outside.”

Police said three of the arrested men were injured in the raids and Mr Causevic said his son’s arm was broken.

“I was in shock yesterday. I just cry all day because when I remember his face … when I came into his bedroom. It’s very hard,” he said.

Police say one of the five men arrested is the subject of a preventative detention order.

Under that act, a person may be detained for up to 14 days.

Victoria Police said it was the first time the provision had been used.

-ABC