The last time Sophie Chang heard from her sister, Diana Lalchan, was Tuesday night, when she called around 10 after a dispute with her husband, Christopher.

The couple had not been getting along and planned to split up, Chang said, but Lalchan, 27, a pharmacist at Walter Reed National Military Medical Center, wasn’t ready for Chris to list his status as “separated” on Facebook.

“I knew they had been fighting, and I knew that things weren’t going well and she was frightened, but she wouldn’t say anything else,” Chang, 25, a student in Massachusetts, said Friday.

Early Thursday morning, just after midnight, court papers say, Diana Lalchan called 911 to report a shooting in the couple’s apartment on Fourth Street SW in the District.

On Friday, police charged Diana Lalchan with second-degree murder in the death of her husband.

When they had arrived at the apartment Thursday morning, they found him in the living room. He had been shot in the back of the head.

At Lalchan’s arraignment Friday, a D.C. Superior Court judge ordered her held in the D.C. jail until her preliminary hearing Wednesday.

According to charging documents filed in D.C. Superior Court, Lalchan waived her rights and told officers that on Wednesday evening, her husband of four years had telephoned her and asked her to return home. Lalchan said that when she arrived at the apartment, she and her husband got into “several arguments.”

During the course of the arguments, Lalchan said, her husband placed a .40-caliber pistol on the TV stand in the living room. Lalchan told police that as her husband walked away from the TV stand, she picked up the gun and fired it at him three times.

Lalchan told police that she was in fear of being attacked and fired the gun as her husband approached her, court papers say. She told them her husband did not physically assault her or threaten her that night, but said she had been a victim of domestic abuse. There is no record in D.C. Superior Court of an abuse case involving the couple.

Lalchan did not have any injuries at the time of her arrest, except for a small bruise on her left arm, court papers say. She told police that she suffered the bruise while training in a martial-arts self-defense class.

Chang said she and her sister grew up in Bethlehem, Pa., the daughters of a physician and his wife who were immigrants from Taiwan.

Diana met Chris Lalchan, a native of Trinidad, at a Maryland church around the time she was getting her pharmacy degree at the University of Maryland Baltimore County.

The couple married and moved to the District, eventually moving into the apartment near the Waterfront Metro station in Southwest. Chris Lalchan, who Chang said worked at Reagan National Airport, loved to cook and usually prepared Thanksgiving dinner for his extended family.

The couple shared a love of the outdoors, Chang said, and Chris Lalchan enjoyed hunting. Police later found three other firearms in Lalchan’s home, including another .40-caliber handgun, a .44-caliber antique black-powder gun and a .38-caliber revolver, authorities said in court papers. They said none of the guns was registered by Diana Lalchan or her husband.

Chang said that in their conversation Tuesday night, her sister would only hint at the disintegrating state of her marriage.

“She felt like things were going to get much worse, and she said she didn’t really want to talk about it,” Chang said.

Police said they have not determined a motive in the incident.

Jennifer Jenkins contributed to this report.