Mike McLelland (centre) answers questions at a press conference in January in Kaufman, Texas

A district attorney has been shot dead in Texas, the third justice official to be killed in the US in recent weeks.

Mike McLelland and his wife were found dead on Saturday in Kaufman County. Kaufman's Assistant District Attorney Mark Hasse was killed in January.

Last week a suspect in the killing of the head of Colorado's department of corrections died in a shootout with police in Texas.

Authorities are investigating whether any of the cases may be linked.

White supremacist group

No arrests have been made over Mr Hasse's killing but police are reportedly looking into a link between his death and the killing on 19 March of Colorado prisons chief Tom Clements.

Speaking of the latest killing, Kaufman Police Chief Chris Aulbaugh told the Dallas Morning News: "It is a shock. It was a shock with Mark Hasse, and now you can just imagine the double shock and until we know what happened, I really can't confirm that it's related, but you always have to assume until it's proven otherwise.''

The lead suspect in Mr Clement's shooting, Evan Spencer Ebel, died in a shootout with police in Decatur, around 135km (85 miles) from Kaufman, on 21 March.

Ebel, 28, was a former Colorado prison inmate and was linked to a white supremacist group in prison called the 211 Crew.

Kaufman County district attorney's office had been one of several agencies involved in the investigation of two members of another white supremacist group on racketeering charges earlier this year.

Mr McLelland had previously had a 23-year career in the army, according the biography on his website, and had five children.