EPHRATA, Wash. -

A Montana man has been convicted of first-degree murder in the shooting death of his former girlfriend's new boyfriend in Ephrata, Wash.

The Columbia Basin Herald reports a jury convicted David Nickels, 31, of East Helena, Mont., of killing Sage Munro, 35, in December 2009. The trial lasted six weeks and jurors deliberated for about five days before returning the verdict on Thursday.

Nickels' sentencing is set for Sept. 18.

Prosecutors alleged Nickels shot Munro because Munro was dating Marita Messick, Nickels' former girlfriend.

Prosecutors alleged Nickels threatened to burn Munro's house down when he first learned about the relationship and later asked a man with a manslaughter conviction if he would kill someone for him.