Montgomery County Courthouse. (Dan Morse/The Washington Post)

Marlon Alexander broke into the apartment, police say, to rape the young woman who lived there alone.

“Don’t move or I will shoot you!” he allegedly yelled.

Alexander was 28, and his target was 25, police said. What he did not know that August night years ago in Gaithersburg, Md., authorities said, was that the woman was a police officer.

She fought off her attacker, and he fled.

It would be 11 years before police caught up to Alexander, prosecutors said in court Tuesday, asserting that his being overpowered by the officer in 2007 had a dramatic impact on a man they described as an inveterate sexual attacker.

“He then chose and targeted elderly women who could not fight back,” said Montgomery County Assistant State’s Attorney Jessica Hall.

Marlon Alexander (Montgomery County Police)

His next two targets, she said, also lived alone: a 68-year-old racked by arthritis and spinal stenosis that limited her movements; an 86-year-old who needed hearing aids.

For Alexander, now 40, the case against him resulted Tuesday in two life terms in prison at sentencing by Circuit Judge Richard Jordan. “The fear and depression and anxiety caused to these women is incalculable,” Jordan said.

Alexander had pleaded guilty to two brutal attacks of the 68-year-old. As part of his plea agreement, prosectors agreed to drop charges in the attacks on the police officer and the 86-year-old.

In court Tuesday, Alexander’s attorney, Victor Del Pino, stressed his client had not pleaded guilty in the attacks of the 86-year-old or the police officer, noting those two cases were being dismissed. Jordan acknowledged that but said prosecutors had the right to detail those allegations as well.

The long investigation that led detectives to Alexander was bolstered by an increasingly common investigative method: comparing DNA left at a crime with known DNA profiles compiled from around the country through the burgeoning ancestry research industry. The goal is to find relatives, even distant ones, and use those identities and genealogy research to track back to a suspect.

Tuesday’s hearing, though, focused on Alexander: his motives in the attacks, other aspects of his life, and whether he deserved a sentence that would give him a decent chance of one day leaving prison.

The police officer who was attacked, now 39 and still on duty with the D.C. police department, spoke in court Tuesday, addressing the judge and Alexander, who sat to her right. “The horror of the night has remained frozen in my mind, frozen in all of your victims’ minds,” she said.

He targeted the 68-year-old victim at 2:50 a.m., stepping into her building and heading up a flight of stairs. Her front door was easy to get through because it had been forced open previously by paramedics responding to a medical emergency.

According to court files, Alexander found the woman in bed and forced her to the ground on her knees where she could not remain because of the pain in her legs. Alexander returned her to her bed and raped her, prosecutors said.

Two months later, prosecutors said, he slipped through the apartment window of the 86-year-old at 4:15 a.m. Armed with scissors, he found her in bed and attacked, according to Assistant State’s Attorney Katherine Getty.

Alexander became frustrated by the woman — who couldn’t hear his commands because she’d taken out her hearing aids — Getty described in court Tuesday, and repeatedly hit her and raped her and climbed back out the window.

The woman called a lifeline medical alert service.

“I just got raped,” she said, according to a recording of her call submitted in court. “I need some help.”

She had trouble hearing the questions from an operator.

“I don’t have my hearing aids in,” the woman said. “I hope he’s gone. . . . I didn’t know if he would kill me or what.”

Five months later, at 12:45 a.m., Alexander returned to the 68-year-old’s apartment, breaking in through a window. From her bed, the woman could see his legs coming through the window.

“You again!” she said on seeing him, as she later told detectives about the second rape.

Talking about Alexander before a sentence was set, his attorney, Del Pino, spoke about his client’s life apart from the attacks.

“Mr. Alexander is not a monster,” Del Pino said. “He is extremely remorseful.”

Alexander grew up in Montgomery County, graduated from high school in Germantown and developed substance abuse problems with alcohol, cocaine and PCP, which spiraled out of control and drove his behavior at the time of the attacks, Del Pino said.

Alexander spoke softly and clearly in court. “I am truly sorry,” he said. “At the time of these events I was in a dark place.”

In the courtroom, his sister leaned her head into the person to her left. Another supporter of Alexander hugged Alexander’s wife.

Del Pino said Alexander has four children and has worked as a warehouse loader, grocery store cashier, and most recently an auto parts salesman at a car dealership.

Del Pino requested a sentence of 18 years and said his client knows he isn’t going home any time soon. “But we do want him to go home,” Del Pino said.

But in court papers filed last week, prosecutors said Alexander’s outward appearance as a working family man allowed him to hide in plain sight: “For the last 11 years, the defendant was able to lead a double life made even more heinous by his ability to hide his crimes from his family.”

That was illustrated by recorded phone calls made from jail by Alexander to his wife, the prosecutors said in filings. “She was unable to reconcile the charges with who she knew her husband to be,” the filings asserted. “She told him that she never got a bad feeling from him.”

According to police affidavits describing his crimes, Alexander managed to enter apartments without being noticed by anyone on the outside. He departed before anyone called the police.

But at four crime scenes, police say, he left DNA. By 2018, advances in genetic matching made it possible to scour databases of other DNA profiles compiled from people around the country who’d submitted samples for ancestry searches and look for a genetic match. Montgomery County police hired Parabon NanoLabs to run such a search, which yielded the names of two people in states outside Maryland who, without knowing it, might be distant relatives of the man who’d left the DNA.

Detectives went to see one of them in Georgia, hoping to learn more about her extended family and learned the woman’s daughter had mapped out an extended family tree with other last names of relatives.

But there was no connection to anyone in Maryland.

A second name provided by Parabon indicated a more distant relative. Montgomery Patrol Officer Steve Smugeresky, an amateur genealogist, worked up a separate family tree for that person, relying on some old-fashioned methods — census data and obituaries — that family-tree builders had used for decades. He found possible relatives in Frederick, Md., and gave those names to detectives working the case.

Using a commercial LexisNexis database of names and addresses, detectives connected one of the names in Frederick to a younger relative living in Germantown, near the crime scenes. His last name rang a bell as a surname the detectives had heard in Georgia: Alexander.

Detectives asked Smugeresky if he could make a genealogical link from the Germantown man — Marlon Alexander — to one of the people in Frederick. He did.

In mid-September 2018, after the careful DNA matching and genealogy work, detectives zeroed in on Alexander. They obtained a DNA sample, matched it to the four crime scenes, and charged him with multiple counts of first-degree rape and first-degree sex offense, according to an affidavit submitted in court by Montgomery Detective Dave Davis.

Detectives also searched Alexander’s home, seizing a laptop, court records state.

The computer contained“numerous pictures of elderly women in pornographic and sexual positions,” prosecutors wrote. Detectives also studied the Internet search history on the computer, which indicated Alexander had been looking for pornography of older women in 2010 and 2011.

He pleaded guilty on Feb. 6 to two felony charges involving the 68-year-old. By then, she was 77 and had moved to Southern Maryland.

Knowing the 86-year-old victim had died years ago, prosecutors went to see the remaining elderly victim. They found her in a bed, owing to her advanced spinal stenosis, in the senior living center where she was a resident. She told them she’d be willing to come to court and speak, even if that meant having to be hoisted on a hospital bed, driven in an ambulance, and staying in Montgomery in a nursing home for a night or two.

Two months ago she, too, passed away.