A St. Louis-area man killed his girlfriend, her two young children and her mother Saturday before exchanging gunfire with police and being shot himself, authorities said.

Richard Darren Emery, of St. Charles, Mo., is charged with a litany of crimes, including first-degree murder, assault and attempted robbery.

He was in a hospital Saturday with two gunshot wounds that authorities said most likely resulted from a shootout with police officers.

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Prosecutors said police received a call late Friday evening about a shooting at a home that Emery, 46, shared with the victims. Prosecuting Attorney Tim Lohmar said officers found three dead victims inside: Zoe Kasten, 8; her brother, Jonathan Kasten, 10; and their grandmother, Jane Moeckel, 61.

"During that phone call, the 911 operator could hear gunshots in the background," St. Charles Police Lt. Tom Wilkison said.

A 39-year-old woman found alive in the master bedroom was taken to a hospital with gunshot wounds but she died. Her name was not released, but authorities said it was the children’s mother.

During a news conference, Lohmar said investigators did not have a motive for the killings.

"We may never know," he said. "This one in particular was the worst example of a domestic violence case. Anytime you have a domestic violence case you worry about the safety of the victim, and this would be your worst nightmare."

After the shooting, Emery tried to flee in his pickup truck but was stopped by police, leading to an exchange of gunshots. He fled on foot and tried unsuccessfully to carjack a woman, stabbing her several times in the process. Her injuries were not life-threatening.

Police eventually arrested Emery several hours later when he sought shelter in the restroom of a convenience store. A store employee called the police.

He faces up to 30 years in prison for each of the charges against him.

Lohmar said that adding more charges and seeking the death penalty are possibilities.

"It's premature for us to make any sort of pronouncement about that right now, but I can tell you this thing looks and smells like a death penalty case," he said.