Isaiah Stephens, 18, and his older sibling - 20-year-old Jay - are charged with assaulting Assistant Commissioner Chris O'Neill, who suffered broken ribs and bleeding on the brain.

Magistrate Duncan Reynolds on Friday said the alleged offending was "serious and disturbing", but agreed to allow Isaiah's release from custody if he adheres to strict bail conditions.

The brothers had been seen drinking heavily before Saturday's alleged attack on Mr O'Neill near Heyington train station.

Police opposed bail, arguing Isaiah was a flight risk because his mother and another older brother live in southwest WA.

There were concerns about his employment status and ability to pay rent, prosecutor Michael Roper said.

Isaiah's father, Jared Pihlgren, had called the factory where the teenager was working and made threats to his boss and fellow workers, police said.

Pihlgren also posted a photo of the employer's wife and children on social media in what was a "veiled threat," Sergeant Matthew Rizun said.

Because of the father's behaviour there was concern about whether Isaiah would be able to return to work at the factory.

But lawyer Greg Thomas argued the employer had not ruled out future employment.

Isaiah moved away from home at age 14 because of problems with his family and hadn't spoken to his father in months, Mr Thomas said.

"He is a young man who has had some serious difficulties to traverse."

Magistrate Reynolds noted the criminal matters could take until 2020 to be dealt with and it was not in the interests of justice or the community to keep Isaiah in custody for a prolonged period.

The youth also had no prior criminal history.

Part of his strict bail conditions include daily reporting to police, a curfew, not to contact his co-accused or father and not to consumer alcohol or take drugs.

The magistrate also noted Isaiah "doesn't have a helpful family environment".

Since Saturday's alleged assault, Pihlgren has been taken into custody, charged with intimidating Mr O'Neill via Facebook.

Australian Associated Press