(CNN) -- A nurse accused of killing a Texas mother in a parking lot and stealing her 3-day-old son had suffered a miscarriage and believed she needed to show her fiance that she had a child, authorities said Wednesday.
A judge refused to allow bond for Verna McClain, 30, a mother of three children.
McClain told her fiance "she was pregnant and had given birth to a child, by him," said Montgomery County Sheriff's Capt. Bruce Zenor. "She represented this (the abducted baby) as her child."
Witnesses said Kala Golden, 28, who was shot outside a Houston-area pediatrician's office Tuesday, screamed and attempted to chase after the car with her son inside, CNN affiliate KTRK reported.
The car struck Golden as it left the scene, the station said. She died later at a hospital. Authorities said she had several gunshot wounds to the torso.
McClain is accused of killing Golden and taking 3-day-old Keegan Schuchardt. She was arrested just before midnight Tuesday, according to an arrest report.
She is charged with capital murder, Montgomery County District Attorney Brett Ligon told reporters.
Zenor indicated the attack on Golden was random. A handgun has been recovered, officials said.
Police believe the kidnapping was the motive for the shooting, the report said. The baby was found safe about six hours later at the residence of the suspect's sister, authorities said. They said they believe McClain acted alone.
"It was a very emotional event for everybody who was there," Ligon said of the recovery of the infant.
Keegan was initially taken into the custody of Texas Child Protective Services, CNN affiliate KHOU reported.
Golden's husband, Keith Schuchardt, told KHOU he had not yet signed Keegan's birth certificate, which complicated the process of getting his son back.
The baby was returned to him Wednesday after the paperwork was resolved, according to Warren Diepraam, Montgomery County district attorney trial division chief.
Schuchardt told the station he was at work when he got a call regarding the shooting. His wife was dead when he reached the hospital, he said.
"It's just a random thing, I think," he said. "We don't have any enemies. I don't know why anyone would do it. Maybe she lost her baby and wanted a baby ... or to sell him. I want to get my baby back."
According to the arrest report, Golden, carrying Keegan, was leaving the Northwoods Pediatric Center in the Houston suburb of Spring when the incident took place Tuesday afternoon.
"The defendant confronted Mrs. Golden and shot her multiple times in the parking lot," then took the baby and left, the report said.
McClain's vehicle was found at an apartment complex, according to the report.
The Montgomery County Sheriff's Office said detectives began a "systematic canvas and search" of areas near the shooting scene and spied the car at the apartment complex. The detectives questioned residents and examined the vehicle, alerting investigators of their findings.
A SWAT team entered an apartment in the complex to search for the baby, the statement said. McClain returned to the apartment as the investigation was continuing and asked to speak to police, the report said.
"She admitted to shooting Mrs. Golden and taking her baby," the arrest report said.
During an interview with authorities, McClain provided information that only someone at the scene would know, the report said.
Evidence was found at both residences and in the car "that support the arrest of the suspect," the sheriff's office said.
McClain's sister, Corina Jackson, told police her sister had said she would be adopting a child soon.
"After killing Golden and kidnapping Keegan, defendant stated to Corina that she now had the child and would be needing to do the adoption, indicating that the abduction of the child was her motive for killing Golden," the report said.
McClain's oldest child is about 16 and the youngest is 6, Diepraam told CNN.
Authorities said Tuesday that Golden and the woman parked next to her at the doctor's office apparently spoke to one another or argued before the shooting.
"They were talking," witness Tia Collins told KTRK. "I did see the lady get out, and they were struggling." She said she heard gunshots and saw Golden fall.
The shooting shocked Houston-area residents. Spring is about 20 miles north of the city.
Jennifer Hartis, a friend of the victim, was one of the many left wondering why.
"She never did anything wrong. She's just a mom doing her best to take care of her kids, and I miss her," Hartis told CNN affiliate KPRC. "Keegan is only 3 days old. He needs to know his mom, and she can't do that now. "
"I'm thinking this is crazy," Frank Johnson of Houston told KHOU. "I'm thinking this doesn't really happen every day in the city. I mean, you hear about a lot of shootings and other types of crimes, but somebody kidnaps a baby, 3 days old, and the mother to be shot? I mean, that's serious stuff. That's really scary."
CNN's Carma Hassan and Nick Valencia contributed to this report.