Bampumim Teixeira briefly worked as a concierge at the building where he is accused of killing two well-known doctors in their Boston penthouse, according to prosecutors.
Teixeira allegedly used his familiarity with the building to lurk around and find the right moment to sneak into the doctors' 11th floor apartment, prosecutors said at a his murder trial this week.
Lina Bolanos, 39, and Richard Field, 48, both anesthesiologists, had desperately tried alerting friends and authorities before they were stabbed to death in May 2017.
Jury deliberation on Teixeira's fate could begin this week. He has pleaded not guilty.
"No video, no audio, no scientific evidence, no credible evidence will tell you that Bampumim Teixeira broke into the home of Lina Bolanos and Richard Field and murdered them," defense attorney Steven Sack argued. "And that's because he didn't."
Here is what we know about the 33-year-old defendant, who was 30 at the time of the killings.
Haunting message on wall at crime scene
Prosecutors said that in the bloodied penthouse where the couple had also been beaten and bound with duct tape police discovered a chilling message scrawled on a wall.
The words "payback" and "he killed my wife," were written out in large letters, Boston Police Department Sgt. Edward Meade testified, according to CNN affiliate WHDH.
Meade also said officers found photos that were crossed out and marked.
"(Field was found) dead in a pool of his own blood. His hands bound behind his back with handcuffs," Suffolk County Assistant District Attorney John Pappas said during the trial, according to CNN affiliate WCVB. "Lina Bolanos was also in a pool of her blood after having been stabbed repeatedly in the neck."
What happened when Teixeira was taken into custody?
Police said at the time of the slayings they were first contacted on the evening of May 5, 2017 by the building concierge, who had been alerted by a concerned friend following a text from Field.
Matthias Heidenreich -- a friend of the doctors -- testified that he received a series of texts from Field asking that he call 911 because a gunman had entered their apartment. He testified that he responded but got no answer.
The messages started "Call 111" -- an apparent reference to 911 -- followed by "Gun man", and "in house" before ending with "Serious," according to the Boston Herald.
Bolanos' godmother, Amanda Gibbs, testified she recognized "Lina's voice" in a phone call to 911 that was played at trial.
In the call, Bolanos' voice was muffled. When she was unable to respond to repeated questions, the operator said she was "releasing the call" and hung up, CNN affiliate WCVB reported.
Field also tried calling for help -- he called 911 eight times, Boston police Sgt. Scott Mackie testified, according to CNN affiliate WHDH.
His phone log showed the calls lasted no longer than two seconds, Mackie testified.
Teixeira was arrested in a building hallway, where he told police there were bodies in the penthouse, Boston police Det. Sean Wallace testified.
"Then he said, 'You guys are going to die.' Then he said, 'They killed my wife.' Then he mentioned something and I heard the word 'sniper,''' the detective told the jury.
Boston police officer Scott MacIsaac testified last month that he shot Teixeira after he saw a silhouette that appeared to be holding a firearm, WCVB reported.
Teixeira was hit in his left hand, abdomen and leg. He was wearing gloves and dark clothing, authorities said.
Outside the apartment, police found a backpack with a replica firearm and jewelry, police said at the time of the slayings. A carving knife and a bright yellow shirt were also found nearby, police said.
Teixeira was arraigned on murder counts in hospital bed
At the time of the killings, a law enforcement source told CNN that Teixeira once held a security job at a building adjacent to the condo complex where the couple lived.
Palladion Services, which provided security and concierge service at the building until early 2016, said in a statement in 2017 that Teixeira worked on the property for about three weeks after passing a reference and background check more than a year ago. He was hired in October 2015; his employment ended in April 2016. The statement did not say why his employment ended or where else he may have worked over the six months.
Teixeira was arraigned on two counts of murder in his hospital bed, tubes crisscrossing his body. His attorney entered a not guilty plea on his behalf and he was ordered held without bail.
Teixiera's eyes were closed for most of the arraignment, though he was able to respond with one-word answers.
Defendant had previous larceny convictions
At the time of the killings, police said there was no evidence connecting Teixeira and the doctors.
Teixeira has two previous larceny convictions, according to Suffolk County District Attorney's Office spokesman Jake Wark. In the summer of 2016, Teixeira passed a note demanding money at a bank.
The second, virtually identical incident, which remained unsolved until Teixeira volunteered the information to law enforcement after his 2016 arrest, took place in August 2014 at the same location, Wark said.
Teixeira pleaded guilty to both crimes and was sentenced to a term of 364 days, with nine months to serve and the balance suspended for a three-year probationary term, according to Wark. No weapon possession or injuries were reported as a part of either incident.
Teixeira moved from Cape Verde in Africa to Boston in 2010
The defendant moved from Cape Verde, an island nation off the coast of Africa, to Boston in 2010 to live with his adoptive mother. But after a year in the United States, at age 24, he abruptly and permanently severed that relationship, Maria Luisa Teixeira told CNN in 2017.
"He said, 'You and I are not getting along anymore' and I asked why? I said, even if I put you in the street, I am your mom," she said.
They apparently lived in the same city but Maria Luisa said they never communicated. He blocked her phone and shunned her efforts at reconciliation, she said. She said she still doesn't know why he left.
Bampumim grew up in Guinea-Bissau, on the west coast of Africa, Maria Luisa said.
She and Bampumim's mother were such close friends they lived together, she said, and she watched him grow from the time he was a 1 year old.
"He was excellent in kindergarten, excellent in school, in religion, in his way of saying 'Hi' to someone, the way he dressed," she said.
After his mother died, she adopted him in 2002, when he was 14, she said.
Maria Luisa said she moved to Boston around 2002, but kept in touch with the teen, who stayed with her sister, she said.
In 2005, he moved to Cape Verde, an island off the coast of Africa, to study psychology at Jean Piaget University.
Maria Luisa described Teixeira as a dutiful son until he left. He didn't smoke or drink alcohol, she said, and he gave her about $150 a week from his paycheck. He was never violent, she said. She heard from others that he was acting strangely after moving out.
Using his Social Security number, she tracked Bampumim to a homeless shelter in Cambridge, she said.
"When they went inside to ask him to come see me, he refused," she said. "So I was very hurt. But anyways, I am a mother. A mother is a mother."
She went back to the shelter a year later and again failed to make contact.
CNN's Christina Maxouris contributed to this report.