A former police firearms instructor gunned down his daughter's partner with a 12-bore shotgun firing twice at close range, a jury has heard.
The deadly incident from May this year at a house in Dartford was recorded as the victim was making a 999 call which was played out to the court.
Accused David Hucker, 69, lived in Dartford Road, Dartford, in a house owned by his daughter.
The murder trial jury at Maidstone Crown Court heard Hucker shout: "I'll boot that door off" and Mr Williamson is heard screaming after the first shot is fired.
He told the 999 operator: "He's just shot me in the ****** chest!"
The court heard how after his arrest Hucker is alleged to have said: "I used to be a firearms instructor for 40 years and worked for the City of London Police and what did I do, shoot the ****** son-in-law?"
Prosecutor Nicholas Corsellis QC said: "These words speak for themselves. They reflect the fact that the defendant was enraged and intentionally killed his daughter’s partner."
He said that Mr Williamson had been visiting Hucker's address and was seen carrying boxes of possessions into it.
The prosecutor alleged that the two men had clashed earlier when Mr Williamson left.
"He returned at just after 12pm and minutes later Mr Williamson went upstairs to get away from the defendant who followed him," Mr Corsellis said.
"Not only that, Hucker took out his shotgun, which he had to hand, and loaded it with not one, but two live cartridges. He then took the safety catch off, making sure it was ready to fire."
He added: "The defendant went into the bedroom where Mr Williamson was on the telephone to the police.
"There he shot Mr Williamson, who was unarmed, to the chest with the first cartridge. He knew he had done so and that Mr Williamson was severely injured and defenceless.
"Sixteen seconds later, he shot Mr Williamson with the second of the cartridges to his neck and head," he alleged.
He told the jury: "The defendant’s principal pastime and hobby was shotgun shooting. He had been involved in the sport for over 30 years and had been a firearms instructor.
"He possessed a number of shotguns and a large amount of ammunition at the house."
The prosecutor said he had been affected by the break-up of his marriage to his daughter's mother in 2018.
"As a consequence he relied on the stability of his home, passion for shooting and his membership of the Masons," the prosecutor added.
But on the day of the shooting the two men fell out over Mr Williamson and his partner planning to move into the house in Dartford Road.
Hucker then later called his daughter and said: "He ain’t ******* moving in here. I will kill him before he moves in here.
"He’s ******* arrogant, he’s got ******* attitude. It ain’t ******* happening. It’s not his house or your house – it’s my house."
The trial continues.