Police have shot dead a 38-year-old man in front of his family north of Hobart, with two children understood to have witnessed the incident.

Key points: Police say they acted in self defence, alleging the man deliberately drove at them

Police say they acted in self defence, alleging the man deliberately drove at them The man had already set fire to part of the home

The man had already set fire to part of the home The matter is being investigated by Tasmania Police's internal investigation unit

An occupant at a home on Tea Tree Road in Brighton called police shortly after 8:00pm on Monday night, saying the man was armed with a knife, acting aggressively and making threats.

Three officers were sent to the address, and police said when they arrived the man deliberately drove at them.

Police Commander Tony Cerritelli said it was then that officers shot at the man.

"We know that there were three police officers … at this stage I'm unsure of how many shots were fired," he said.

"We know at least one shot was fired."

The man died on the driveway of the property.

It is understood two children witnessed the shooting.

"This is a tragic event for all involved, including the male, the family, the attending police, all emergency workers, so it's a terrible event and there's no winners out of it," Commander Cerritelli said.

He said officers' decision to open fire was not one that was ever made lightly.

"We train for those sorts of events, but you train with the view of never having to use it. It is such a large call," he said.

"The police officers that attended … I'm advised that they believe that their life was at risk, a direct threat. And that's why they took the action they did."

The man had already set fire to part of them home and firefighters were also called to the property.

It is understood it was not the first time police had been called to a disturbance involving the man.

Tasmania Police's internal investigation unit, Professional Standards, is investigating the shooting. It is also the subject of a coronial investigation.

Commander Cerritelli said it was important there is "independent oversight" during the investigation.

"We'll be making sure that the investigation is conducted professionally and at arm's length, with the coroner having input as well," he said.

No officers were injured during the incident.

Police said the officers, as well as the man's family, would be offered counselling and support.