Mr Simpson said the 33-year-old had battled mental health issues for several years.
Mr Te Moananui was shot by police at a house in Thames on Saturday afternoon, and died soon after.
A grandfather, he lived in nearby Kopu, where police were initially called for assistance about midday.
He left the property and was found at his sister's house in Campbell St, Thames, by the Waikato armed offenders squad just before 4.30pm. He was in an agitated state.
Witnesses, relatives and neighbours heard shots fired before watching the squad members storm the garage.
Mr Te Moananui was given CPR before St John Ambulance staff took him away on a stretcher. He died soon after in Thames Hospital.
His body was returned to his whanau yesterday after an autopsy in Auckland.
Mr Simpson said despite Mr Te Moananui's tough appearance, he had a kind heart. But he struggled with the thoughts in his head.
"He was soft [guy], but he had issues. He'd had demons haunting him for years and that's the reason why he did what he did. But he loved his mother and he loved his family. He just couldn't take the pressure and things were just going against him.
"We don't actually know too much what happened. We were dealing with ongoing issues with Vaughan so we know that there were things there, but we don't know what drove him to it, we don't know what the final straw was.
"He was with family when he did it; he'd just arrived there when he did it."
Mr Simpson said they still wanted clarification from the four official investigations that were now under way.
"We know pretty much what happened in ourselves but we need to have an official version. We're not holding any grudges against police, that's the main thing."
He said Mt Te Moananui also hadn't held any grudges against them. "He was just a lost soul. He didn't intend on hurting anybody. [It can't have been] nice for anyone else to see, and even the police with having to deal with it."
Next-door neighbour Win Castle said she, her husband, Alick, and friends from Auckland watched the drama unfold from their lounge.
"We were able to see the armed offenders [squad] take a couple of pot shots at the house and then them all running towards the house where [Mr Te Moananui] was."
Mrs Castle said they saw armed officers fire what they believed to be two shots into the garage from across the road and, shortly after, they heard two more.
Detective Inspector Chris Page said Mr Te Moananui had been called on to surrender but instead had presented a firearm at police, at which point they fired at him.
Police would like anyone who interacted with Mr Te Moananui recently, or saw any of the events on Saturday, to phone the Thames station on (07) 867-9600.
