A barely legible message scrawled on a shoebox lid and thrown from a bedroom window during the Chelsea siege encapsulated Mark Saunders’s confusion and despair.

Written in black marker pen were the words: “I love my wife dearly xxx.”

But Elizabeth Clarke had decided, because of her husband’s increasingly drunken and erratic behaviour, that she could no longer love him or live with him.

An argument that caused Miss Clarke to run from the house in tears about 4pm set off the extraordinary series of events that ended with police marksmen shooting Mr Saunders dead at 9.30pm.

Mr Saunders, 32, and Miss Clarke, 40, were both highly paid and sought-after family lawyers, working from the Queen Elizabeth Building chambers in the Temple. They had been married for less than two years.

She was tipped to become a Queen’s Counsel soon and was spoken of in legal circles as a future judge in the Family Division. The Chambers legal directory said that he was noted for his “maturity, unflappability and lack of hesitation”.

They lived in a townhouse just off King’s Road, one of the country’s most famous and fashionable streets.

Mr Saunders, a former trooper in the Honourable Artillery Company, reacted to the row with his estranged wife by drinking heavily then taking his shotgun from its locked cabinet and firing out the bedroom windows at neighbours in Markham Square.

Police were called and 30 armed officers surrounded the building. In the hours that followed, nine of those officers returned fire at Mr Saunders.

The barrister had a shotgun licence and a legally held firearm was found in his home after police forced their way in.

Jane Winkworth, who lived in the basement flat below Mr Saunders’s house, was in her back garden when he began shooting.

She said: “I was shouting and screaming at him to stop. At first I assumed that he was using an airgun to shoot at pigeons, but after he fired two more I realised that it was a proper gun.”

In a house behind the square, Leslie Hummel was having a late lunch with a friend when they heard three loud “pops”. She said: “I ran into see what damage he had done, and he had been shooting into my daughter’s bedroom. He didn’t bother to open the window, he was just shooting out. I could see the tip of the gun.”

Mrs Hummel took a police officer to the bedroom and saw brick dust fly up as a shot whizzed into the room, 3 feet from where the officer was standing. She said: “The policeman was very lucky. He reacted and returned fire with a handgun.”

About 7pm Mr Saunders threw the message for his wife out the window into Ms Winkworth’s garden.

Further shots were exchanged between the gunman and police about 9.10pm before the final fatal confrontation at 9.30pm.

Witnesses reported seeing police marksmen taking aim at Mr Saunders. Marie Morgan Rees, 48, a member of Neighbourhood Watch for Markham Square, said that police appeared to shoot through the window from a balcony on the opposite side of the square. Later witnesses saw green flashes, indicating that police were using stun grenades to enter the property. It is understood that they found Mr Saunders lying on the floor, with a shotgun by his side, and carried him outside, where paramedics administered first aid.

Friends of the couple said that they married in August 2006 but separated a few months ago.

One said: “Liz is extremely sensible and sweet, but he had an extremely wild side and could not be tamed. He loved her very much but could not contain his greater love of red wine and whisky, and at all times of day.

“While they spent so much of their lives examining other people’s marriages, they could not seem to reconcile their own.”

They met at work, where both specialised in matrimonial finance, often dealing with wealthy and prominent clients. Colleagues were surprised when they became an item more than three years ago.

He was educated privately at Kings School, Macclesfield, and then studied law at Christ Church College, Oxford. His father, Rodney, is a chartered quantity surveyor. She was a comprehensive-school girl, the daughter of a printer from Leicester whose academic ability took her to Lady Margaret Hall, Oxford.

The couple married at Chelsea Register Office and bought the leasehold to their three-floor property last September for £2.28 million, according to Land Registry documents.

Mr Saunders’s father, speaking from the family’s home in Alderley Edge, Cheshire, said that he was in a state of shock over the incident. “It is an absolute mystery. In some ways it would help if we could find out what went on and why he has done it.”

His wife, Rosemary, said: “We’re still trying to come to terms with it.”

The Independent Police Complaints Commission has begun an investigation into the shooting. Yesterday afternoon a postmortem examination was carried out on Mr Saunders’s body.

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