WARMINSTER TWP., Pa. -

The Bucks County District Attorney has filed additional charges against a man who triggered a deadly standoff.

D.A. David Heckler has charged Andrew Cairns with criminal homicide.

He said even through police shot and killed Marie Zienkewicz, it was Cairns'  actions that led to her death.

The 89-year-old woman was killed last month during a standoff at an apartment complex in Warminster.

Heckler said police mistakenly shot her when she opened her door during a shootout and reached for Deborah Silva, Cairns' ex-girlfriend.

Police said the standoff followed an argument between Cairns' and Silva.