Two men have been charged in an ambush at a backyard cookout that left a pregnant women, her 8-month-old fetus and four other adults dead near Pittsburgh.

Authorities have charged 29-year-old Cheron Shelton and 27-year-old Robert Thomas with six counts of criminal homicide for the March ambush in Wilkinsburg.

Police have said that one gunman fired into the yard, prompting partygoers to huddle by a rear porch where a second gunman shot them with a rifle from behind a fence.

The victims include a woman who lived at the home and her two adults siblings. A medical examiner ruled the fetus' death as one of the six homicides.

Both suspects have been in custody on other charges. Their attorneys say they've seen no evidence the men were involved.

Prosecutors say the target was wounded but survived.