The son of a Pembrokeshire man accused of two double murders said his father would go for long evening walks with a shotgun under his jacket.
Andrew Cooper told Swansea Crown Court his father, a farm labourer, from Letterston, would disappear for hours.
John Cooper, 66, denies murdering Richard and Helen Thomas in 1985 and Peter and Gwenda Dixon in 1989.
He also denies charges of rape, indecent assault and five attempted robberies in 1996.
Gwenda and Peter Dixon from Oxfordshire, were on a camping holiday in Pembrokeshire. Their bodies were found on the national park coastal path. They had been shot.
Between those dates Mr Dixon's bank card had been used to withdraw money from cash points at banks in Pembroke and Haverfordwest.
Four years earlier, Richard and Helen Thomas were found shot dead at their house Scoveston Park, near Milford Haven.
Appearing as a prosecution witness, Andrew Cooper said while growing up his family lived in a number of houses in Pembrokeshire including Jordanston, Rosemarket and Hazel Beach.
He described Mr Cooper, a farm labourer, as "very strong," "very fit," and a "loud aggressive man."
He said part of his father's routine was to go for long walks, usually after tea and would sometimes have a shotgun "on a piece of string" around his shoulder, concealed under his jacket.
Andrew Cooper told the court how his father kept his belongings in a locked room.
He said one time he went in when his father was not there he found in a metal cupboard what "looked like other peoples' possessions".
Those included photographs of people he did not know, trinkets, and burned jewellery and coins.
There was also the barrel from a sawn-off shotgun in a vice.
On another occasion, he described finding a briefcase full of silver ornaments.
Mr Cooper was shown a photograph of a double-barrelled gun which the prosecution say was found near the scene of a robbery his father was convicted for in 1998.
The prosecution says flecks of Peter Dixon's blood were found on the gun.
Mr Cooper told the jury it looked very similar to the one his father would carry and that the attached clip and cord used to be his mother's dog lead.
But under cross examination by defence barrister Mark Evans QC, Mr Cooper admitted that when he was shown different images of the same gun by police in 1998 and 2008 he had not recognised it.
Mr Evans put it to Mr Cooper, who appeared via video-link, that his testimony to the jury was "not the truth".
While being questioned by Mr Evans, Mr Cooper said his relationship with his father was "bad".
He told the court he first moved out of the family home when 16 and that for five years in the 1990s he hardly had any contact with his family.
On Wednesday, the jury were told how Mr Cooper is accused of cornering five teenagers in a field in 1996 and raping one of them.
He is accused of indecently assaulting another and demanding money from them all.
The trial continues.