A GUNMAN who murdered a business associate and injured the man's son in a shooting at an equestrian centre had once amassed a collection of guns and army paraphernalia, it has been claimed.

Robert McCormick, 53, took his own life with the shotgun he used to kill farm owner Peter Thompson, 59, and shoot his son John, 36, in the leg.

He was described by one man who knew him as a 'bit obsessed' by the weapons.

Mr McCormick is thought to have been motivated to murder Mr Thompson as his victim is believed to have owed him thousands of pounds.

He is said to have owned a machine gun, a Czech Army pistol and other guns in the 1980s. It is not clear whether he still had the arsenal at the time of the tragedy.

The source said: "When I knew Robert, back in the 1980s, he had an arsenal of weapons.

"He had a vast collection of guns, everything from a machine gun to a Czech Army pistol. He had a lot of army gear.

"I would say he was a bit obsessed with guns."

On earlier reports Mr ­McCormick, who lived on his own, was a loner, the former associate added: "He never socialised with anyone and could be a bit of a bully, he trampled all over people."

Mr McCormick's younger brother John also died from gunshot wounds back in 1984. He was found in his Glasgow home with fatal head injuries aged 21.

The associate said: "You'd think if your brother killed himself with a gun you'd never want to see a gun again, never mind have them in your home."

The acquaintance said he instinctively knew Mr McCormick was responsible for Monday's shootings at Meadowhead Farm and riding school in Auldhouse, near East Kilbride, South Lanarkshire.

He added: "As soon as I heard about the location and nature of the incident, Robert McCormick came to my mind. I thought to myself 'could Robert have done this?' And sadly I was right."

It is alleged Mr Thompson refused to pay Mr McCormick, of Clarkston, East Renfrewshire, thousands loaned to him over a 10-year period, including a reported lump sum of £100,000, leaving Mr McCormick penniless.

The gunman was said to be depressed over money worries and a financial dispute with Mr Thompson, and is thought to have feared sheriff officers were coming to his house next week.

He reportedly sent a farewell text to his sister Margaret before the tragedy.

At Mr McCormick's semi-detached home, police spent the day searching inside the property and a number of officers were seen entering and leaving the premises. Armed police had gone there within an hour of the shooting and an officer has remained stationed outside.

Yesterday, plain-clothed ­detectives were seen leaving Robert McCormick's terraced home with bags of evidence. The sealed bags taken from the property appeared to show materials linked to firearms and telescopic sights.

Mr Thompson senior had split from his wife Caron two years ago and she has since started a new family.

John Thompson, has been released from Hairmyres Hospital in East Kilbride, where he has been receiving treatment.