A British security contractor being held by Iraqi police on suspicion of murdering two of his colleagues had been back in the country for a matter of days.
Danny Fitzsimons allegedly shot dead fellow Briton Paul McGuigan and Australian Darren Hoare in a "squabble" inside Baghdad's Green Zone.
A second British employee was questioned by Iraqi police but was subsequently released.
Ex-Royal Marine Mr McGuigan, 37, has relatives in the Bordcers area of Scotland and had worked for the company in Iraq for six years
Fitzsimons re-joined ArmorGroup Iraq at the end of July, said a spokesman for the company Patrick Toyne-Sewell.
He had worked as a contractor for various companies in Iraq since 2004 and last year "took some time out" before returning.
Fitzsimons could become the first Westerner to face an Iraqi trial on murder charges since an agreement giving foreign workers immunity was lifted.
He is also accused of wounding an Iraqi as he tried to flee the scene of the attack in Baghdad's International Zone on Sunday morning.
Iraqi military spokesman Major General Qassim al-Moussawi said: "It started as a squabble. The suspect is facing a premeditated murder charge. The matter is now in the hands of Iraqi justice."
Mr Toyne-Sewell said ex-Royal Marine Mr McGuigan, 37, had worked for the company in Iraq for six years. His parents live in the Peebles area of the Scottish Borders and most recently headed up a team tasked with "personal security".
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