On Christmas Day, Tricia McCauley made a pie and prepared her signature Brussels sprouts to take to a holiday party with fellow members of the District’s theater scene. At 4:30 p.m., she posted on Facebook that she was on her way.

She never showed for dinner.

A frantic search by friends and family, scouring city blocks, ended just after midnight Tuesday, when a man walking his dog near Dupont Circle spotted McCauley’s white two-door Scion iQ with its “Plant more plants” bumper sticker. He called police.

Police found the car a few minutes later parked in the 2200 block of M Street NW in West End. In a nearby CVS store, they confronted a man who had been spotted driving the Scion. A police report says that an officer asked the man for the keys and that he surrendered them. Inside the car, police found McCauley’s 5-foot-4, 115-pound body.

Tricia Lynn McCauley, 46, of Washington, D.C. (Courtesty of Metropolitan Police Department)

[‘Everybody had a crush on her’: Before she was killed, Tricia McCauley radiated light]

McCauley had been strangled and beaten, authorities said. Police charged the man, Adrian Duane Johnson, 29, with first-degree felony murder, among other crimes.

Police said they don’t know how the 46-year-old McCauley first encountered Johnson. The two were strangers, police said. Interim D.C. police chief Peter Newsham said detectives don’t know where or when McCauley was killed.

Johnson has a long record of arrests, mostly for theft and nonviolent crimes, in the District, Maryland and Virginia. Court files contain notations of possible mental illness, though he has been ruled competent in the past.

Russell Dixon, Johnson’s stepfather, said Johnson had been living on the streets and suffered from mental problems. But Dixon said he never saw any signs of violence.

“I never saw any aggression,” he said.

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Dixon said Johnson’s mother, Marlene, had tried to help her son. He suggested that the courts had been too lenient on his stepson. “The court system let him go. That’s not the help he needs,” he said. “He should have been held.”

Marlene Dixon was unaware that her son had been arrested.

When she heard he was a suspect in a killing, she responded: “No, no, no, no, no.”

Earlier this month, Johnson was arrested at a CVS store in the Columbia Heights neighborhood and charged with stealing four electric toothbrushes. Court records show that Johnson was ordered detained in that case on Dec. 17. But at a Dec. 20 hearing, the records state, “the government did not have a witness and was not ready to proceed.”

The court docket says prosecutors urged a judge to release Johnson into the most restrictive monitoring possible, which typically requires defendants to be confined to their homes. Johnson’s attorney told the court that her client required mental health screening, which he could not get under the restrictive program.

The judge ordered Johnson released with GPS monitoring, ordered him to stay away from the CVS and to seek mental health screening. A law enforcement official said Johnson did not show up as required Dec. 21 to have the GPS device secured on his ankle. There is no indication in the court file of any follow-up.

McCauley’s death has hit hard people whose lives intersected with her diverse world — professional acting, yoga instruction, herbalism, running Leafyhead Lotions and Potions, and urban gardening.

When McCauley didn’t show Sunday for the annual party hosted by Bill Largess, the artistic director for the Washington Stage Guild, guests didn’t worry immediately. She had slept through a similar dinner in the past. It wasn’t until Monday morning, when she failed to board a plane to Oregon to visit family for the holiday, that real concern set in.

Friends began a search and set up a Facebook page run by McCauley’s brother. Ann Norton, the executive director of the Washington Stage Guild, went to McCauley’s apartment on North Capitol Street. Roommates were gone; she found the apartment “neat as a pin,” though McCauley had left behind an unwashed pan with the scrapings of her Brussels sprouts, caramelized in balsamic vinegar.

It was a clue that McCauley had left for the party and taken her food.

What happened in the ensuing hours remains unknown.

Police said they tracked Johnson to several locations Monday, including spots on Georgia Avenue in Northwest, Fourth Street near the courthouse and on Rhode Island Avenue in Northeast. Between 8 a.m. and 8:30 a.m. that day, Newsham said, Johnson was inside a CVS store near Union Station. Newsham said Johnson assaulted a worker and stole some items; McCauley’s car was nearby.

At 10:21 p.m., D.C. police issued a “critical missing alert” for McCauley, with a picture of her and descriptions of her car and a man who may have been seen driving it. It flashed on Jonathan Padget’s phone as he walked his dog about midnight near 21st and P streets Northwest. He knew McCauley through his involvement in D.C. theatre.

Padget said he saw a white car parked on P Street with a man in the driver’s seat smoking a cigar or cigarette, with music blaring. “He was bouncing around to the music,” Padget said. “He was looking directly at me.”

Padget, a freelance writer, said the man stuck his head out the window and angrily asked, “Hello, sir, how are you?” He then drove off, but not before Padget noticed that the license plate matched the one on the police alert. He called police, who found the car three blocks away.

Several hours later, McCauley’s brother, Brian, posted on Facebook: “Tricia is gone, they have found her body. Thank you all for your work, support and love.”

On Tuesday evening, people gathered inside the tiny D.C. yoga studio where McCauley taught. The group of about 100 gathered candles and walked to LeDroit Park Community Garden where the actress tended to plants and herbs.

Jim Zidar held his candle steady even as his emotions welled to the surface.

“She was an utterly fearless artist,” Zidar said.

Jennifer Jenkins, Ian Shapira and Victoria St. Martin contributed to this report.