Prosecutors say a St. Louis-area man charged with fatally shooting his girlfriend, her two young children and her mother may face the death penalty once the investigation is complete, Associated Press reports.

Richard Darren Emery of St. Charles, Missouri, is facing 15 charges, including first-degree murder.

ST. CHARLES, Mo. (AP) — Prosecutors say a St. Louis-area man charged with fatally shooting his girlfriend, her two young children and her mother could face the death penalty once the investigation is complete.

The St. Louis Post-Dispatch reports that authorities are still investigating what led to the shooting late Friday. Richard Darren Emery of St. Charles, Missouri, is facing 15 charges, including first-degree murder.

Emery, who often goes by his middle name Darren, exchanged gunfire with officers as he fled. He was captured several hours later — wounded and covered in blood.

St. Charles is a city of about 70,000 residents on the Missouri River northwest of St. Louis.

A St. Louis-area man shot his girlfriend, her two young children and her mother in the home they all shared, authorities said Saturday. AP

A candlelight vigil was planned Sunday evening to honor the victims: 61-year-old Jane Moeckel, 39-year-old Kate Kasten, 8-year-old Zoe Kasten and 10-year-old Jonathan Kasten.

Emery remained in a local hospital with two gunshot wounds that authorities said did not appear self-inflicted and most likely came from the shootout with officers.

St. Charles County Prosecuting Attorney Tim Lohmar said investigators did not know the motive for the shootings as of Saturday evening.

"We may never know," Lohmar said during an earlier news conference. "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."

The initial call came to police came from inside the house, and Lohmar said investigators believe Moeckel made it.

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

Lohmar said Emery attempted to flee in his pickup and was stopped by a police car. He and the officers exchanged shots, and he fled on foot.

Authorities described his attempt to steal another vehicle as a carjacking and said she stabbed its female driver seven times. They said her injuries were not life-threatening.

The area is wooded, and Lohmar said Emery was able to elude police in the dark. But when he sought shelter in the bathroom of the convenience store a few miles away, an employee contacted police, Lohmar said.

Each of the charges against Emery carries a possible penalty of 30 years to life in prison, Lohmar said, adding that more charges are possible and seeking the death penalty is an option under Missouri law.

"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.