A man whose trigger rage is described as a "red mist".

Who once punched a sibling in the face so hard that the youth was knocked out cold, according to his brother.

Who began using steroids as a teenager — synthetic drugs linked to aggression and uncontrollable wrath, his brother said.

Who strikes fear in the heart of family members.

Father of 18-year-old triplets who must now come to grips with the fact their police officer dad has been shot full of bullets — at least five, his life saved by a Kevlar vest.

Const. Nathan Parker, a veteran with 28 years on the force, was the "victim" in Thursday's cop-on-cop shooting between officers with the Niagara Regional Police Service.

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Det.-Sgt. Shane Donovan, identified as the cop who fired his police-issue gun, has been designated the only "subject officer" by the Special Investigations Unit, arising from a violent confrontation, purportedly a fist fight, during what should have been a routine followup — reconstructing the scene — of an impaired driving collision 17 days earlier, down a rural road about 22 kilometres south of St. Catharines.

"Nathan Parker is no innocent person," his brother Phillip Parker told the Star on Sunday. "I can tell you … that if he got shot, it's because he made the other person fear for his life. He's a frightening person."

In a phone interview and email communications, Phillip Parker recounted a lifetime of bullying, threats and physical violence at the hands of his three-years-older brother, leading ultimately to complete estrangement in 2012. "I won't let him anywhere near me and, more importantly, I won't let him anywhere near my daughter."

Philip Parker writes: "As a family member, I am supposed to be shocked and filled with emotion, but my first reaction is, 'What took so long?'

"My brother is a violent man. Niagara should have fired him years ago. Maybe the other officer will face real consequences. Then again, maybe he was defending himself from my brother and his uncontrollable rage. I was on the receiving end of that rage while growing up, so my assumption leans toward self-defence."

One of the final episodes in which the brothers had contact was when Philip Parker's ex-wife tried to arrange a get-together with their kids. Nathan Parker responded with increasingly hostile emails accusing his sister-in-law of maintaining a friendship with his own "f---ing" ex-wife. The Star has seen some of those emails.

"I'm the one who deserves an apology and bring up my job again Phillip oh ya … you don't have one right. Have a nice life … because obviously you think more of someone who abandoned me because she listened to other people … siding with people outside your family that's integrity is it …"

Nathan Parker accused his ex's sister of "badmouthing" him around Niagara region, "which even interfered with my job."

Phillip Parker countered: "Is your reaction to rage until you suffer an aneurysm? Anger hurts only you and the kids … Do not forget, I grew up with your bullying, so I do possess some insight. Bellowing and impulsive aggression mark your pattern of behaviour. Roaring and screaming works for drill instructors, but it alienates and terrifies your family."

To the Star, Phillip expressed regret that he hadn't brought his concerns about his brother's anger management issues to the police department. But Niagara Regional has been well aware of Nathan Parker's history, which includes four disciplinary hearings involving aggressive behaviour and unreasonable use of force. In all cases he was either convicted by a tribunal or pleaded guilty. Collectively, the constable has been docked 226 hours pay since 2012. At one point, he was also ordered to take retraining and anger management counselling.

Phillip Parker suggests "it is more expensive to set legal precedent and fight the police union than it is to keep Nathan Parker on the payroll. That is my ignorance, suspicious opinion, since I have no law enforcement experience. But how else can someone explain my brother not getting fired after (a) cyclist was picked up and thrown to the pavement on his bike, with his feet still clipped into the pedals? Appalling and self-evident. Niagara Regional Police is in dire need of fresh leadership."

In fact, while this is believed to be the first allegedly deliberate cop-on-cop shooting, possibly in the entire country, a Niagara Regional officer was killed by a fellow cop during training at the police firing range in 1993. And last year, a constable pleaded guilty to pointing an unloaded police rifle at a fellow officer's chest in their detachment in what was apparently a jest. She pleaded guilty and was given an absolute discharge.

Nathan Parker is reported in "stable" condition in hospital. The Toronto Sun's Sam Pazzano has reported that the officer who fired emptied most of his 15-bullet magazine at his fellow-cop during the "altercation," as described by the SIU, and that Parker had a portion of his nose blown off.

The SIU has designated 13 cops (including Parker) as witness officers, which, as an aside, begs the question: Why was there practically an entire platoon at the scene?

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Two firearms, belonging to Parker and Donovan, were retrieved by SIU investigators. As of Sunday, no charges had been laid.

But Phillip Parker asks a crucial question: Why was Parker, given his troubling history, still a cop, authorized to carry a weapon?

In Ontario, under the Police Services Act, tribunals can be held at the behest of a police chief but the chief cannot unilaterally dismiss an officer unless he or she has been convicted of a criminal offence.

"The chief is removed from the hearing to make it fair and impartial," explains Cliff Priest, president of the Niagara Regional Police Association. "The chief has to follow the Police Services Act, which means there has to be a hearing. The tribunal decides on the resolution. At times, it can result in dismissal and (the punishment) can be accumulative."

Yet the Act itself is deeply flawed, says Alok Mukherjee, former chair of the Toronto police board.

"A police chief can recommend dismissal to the board, based on severity of the offence (under the PSA). The problem is that doesn't happen as frequently as one would hope.''

One reason for that is because hearings are conducted by senior officers — who aren't trained judges or lawyers — from within the same police force of the defendant. While there are distinct "principles" to ascertain guilt and consequences, tribunal officiators tend to "apply low standards," says Mukherjee.

Changing the Police Act to address that concern "has been a topic of conversation", Mukherjee continues. "This system of imposing discipline is so out of date and so difficult to apply that it needs to be changed. It is a very unsatisfactory system."

Mukherjee further asserts that the SIU — which investigates all incidents involving police that result in death, serious injury or allegations of sexual assault — "tends to frame its investigations too narrowly.

"The SIU does have the ability to cast its net wide, take a broader view in justice oversight, but it doesn't do that."

Mukherjee can't speak specifically to this cop-on-cop shooting. But he echoes the concern of Phillip Parker. "If there was a history with this officer, why was he able to get away with it for so long?"

Phillip Parker doesn't much care what happens to his brother now. "My brother had bad blood with the world.

"You report that monster was in critical condition. I feel concern for his three kids."

Rosie DiManno is a columnist based in Toronto covering sports and current affairs. Follow her on Twitter: @rdimanno