BUTTE, Mont. -

Police arrested Jeffery Lackman and Juan Jose Romero outside of Roundup in eastern Montana just after midnight on Wednesday morning.

Lackman has been charged with deliberate homicide in the shooting death of 46-year old Mark Partelow. Prosecutors charged Romero with deliberate homicide by accountability.

Prosecutors didn't offer a possible motive for why Lackman allegedly shot Partelow, but they do accuse Romero of driving Lackman to Partelow's house. Then, as Butte police tell us, an argument ensued in the yard.

They say Lackman shot Partelow in the head, and he and Romero allegedly raced off. The two made it all the way to Roundup, where troopers arrested them.

In court Wednesday, the two men were read their charges.

Lackman is charged with deliberate homicide, while Romero is charged with deliberate homicide by accountability.

Lackman is being held on a $500,000 bond, and Romero, $250,000.