There's more about it in this article part of which says (my emphasis):         


Gunmen kill Iraqi tribal chief

Relatives mourn Khadim Sarhid Hemaiyim

Dozens have gone to Khadim Hemaiyim's home to mourn
Gunmen have shot dead a prominent Sunni Arab tribal chief, his three sons and a son-in-law as they slept in their home in Baghdad, police say.

Khadim Sarhid al-Hemaiyim was the leader of the al-Batta tribe, a branch of the al-Dulaym tribe, one of the largest Sunni tribes in Iraq.

Officials said gunmen dressed in Iraqi army uniforms broke into his house and opened fire with automatic weapons.

The killings are the latest in a series of attacks on Sunni Arab leaders.

The gunmen arrived at the house in Baghdad's south-eastern al-Hurriya district at 0400 (0100 GMT) in 10 armoured cars similar to those used by Iraqi security services.

"I saw it with my own eyes. They were soldiers," Mr Hemaiyim's son, Thair Khadim Sarhid, told Reuters.

Mr Sarhid said that he and two of his dead brothers were policemen.

"I am going to get rid of my police badge. From now on I will be a terrorist," he said.

Army denials

Sunni leaders have frequently accused Shia militias within the Iraqi security apparatus of operating death squads with a sectarian agenda.

A spokesman for the Iraqi military said that its forces were not involved in the killing and that it was likely to have been militants in disguise.

"Surely, they are outlaw insurgents. As for the military uniform, they can be bought from many shops in Baghdad," Maj Falah al-Mohammedawi said.

He also had another son murdered just one month ago.

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