Now the officer was contemplating leaving the police.
"[He is] feeling sick with anxiety and his wife and children worry about him every time he is out at night doing his job," Judge Phillips said.
Waimate man Dempsey had previously pleaded guilty to eight charges — including weapons, driving and sex offences — and was jailed for four and a half years yesterday.
Because he was convicted of a first-strike offence in 2011 — sexual connection with a 14-year-old girl — he will serve this entire prison term without chance of parole.
On October 2 last year, Dempsey had just finished a spell on parole following a period of incarceration for exposing himself to young girls.
The defendant was riding his bike around Victoria Park when he saw four children, aged between 6 and 11.
After circling them, he rode to a toilet block and exposed his genitalia, beckoning at them as they walked past.
When Dempsey returned home, he became agitated after a family member quizzed him about his movements, and used a knife to open a gun safe.
Removing the .22 Ruger rifle and grabbing 133 rounds of ammunition along with two petrol drums, he set off in his red BMW.
By 6pm he had stolen $237 of fuel from a Palmerston service station.
The theft was clearly planned, Judge Phillips said, since Dempsey had changed the number plates on his car.
Police saw him more than an hour later, driving through Milton, and began the pursuit.
When the defendant spotted them, he took the rifle from the back seat and loaded it.
Entering Balclutha, police activated lights and sirens while laying road spikes in Dempsey's path, but he swerved into the wrong side of the road to avoid them.
At speeds reaching 140km/h, he zipped through the town before losing control and crashing into a ditch in Barnego Rd.
An officer pulled up 50m from the scene. Dempsey walked towards him, pointed the weapon and fired.
It failed to discharge and the officer reversed at speed.
Despite the failure, the judge said the intent was clear.
"The gun was loaded, cocked and ready to fire," he said.
Moments later, Dempsey reloaded and fired the rifle into the ground.
When he gave himself up soon after, he admitted he was considering "committing suicide by cop".
Dempsey said he knew he was in trouble for exposing himself to the children earlier and "just wanted to get away from everyone".
Counsel John Westgate said his client did not specifically aim the firearm at the police officer.
He was rather pointing in his "general direction", he said.
The court heard Dempsey did not consider his lewd acts to be sexually motivated and he believed he should be given a therapeutic sentence rather than imprisonment.
Judge Phillips disagreed.
He said both the police officer and the four children would be severely and irreparably damaged by the ordeal they endured.
As well as the jail term, Dempsey was also banned from driving for a year.
October 2, 2017
• 3pm: Ben Dempsey rides his bike to Victoria Park, in Waimate, exposes himself to a group of four children by a toilet block and gestures for them to join him.
• Returns home, tells family member he had not been at the park, forces open gun safe and leaves home with .22 rifle 133 rounds of ammunition and empty petrol containers.
• 5.55pm: After changing the number plates on his car, Dempsey fills the drums with $237 of petrol and leaves Palmerston service station without paying.
• 7.22pm: Police see Dempsey driving through Milton, follow discreetly but the defendant sees them and loads the rifle as he drives.
• Dempsey avoids road spikes in Balclutha and speeds off at 140kmh before crashing into a ditch.
• He aims at a police officer 50m away and fires but the weapon fails to discharge.
