But after a year in the United States, at age 24, he abruptly and permanently severed that relationship, Maria Luisa Teixeira said.
"I came back from Brazil and one week later he said he was going to move out," she said in an interview with CNN. "And I asked why? 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."
That was six years ago. During that time, they apparently lived in the same city but Teixeira says 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.
Her deep hurt turned to shock last week when Bampumim Teixeira, now 30, was named the chief suspect in a bloody and bizarre crime that shook Boston.
He is accused of killing Richard Field, 49, and his fiancée, Lina Bolanos, 38, on May 5 inside the luxury high-rise in South Boston where they lived. Both were well-known anesthesiologists in the region. Bampumim Teixeira was apprehended at the crime scene.
Maria Luisa Teixeira said she has no idea what happened.
'He was excellent'
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 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.
A spokesperson for the school said Bampumim was an average student, friendly and well-liked. He attended the school from 2005 to 2009 but didn't receive a diploma because he left before completing his final project thesis, said the spokesperson, Filomeno Vega.
Maria Luisa said she visited Cape Verde to check on him and his twin sister, Carlota Gomes, who told CNN Bampumim was an easygoing sibling who loved to sing.
Around 2010, Bampumim moved to Boston to live with her, Maria Luisa said.
'No, you're confused'
Before he left her home, Bampumim was a dutiful son, she said.
"He would work, he would go and [give me] $150 every week, every Tuesday," she said. "I would say why and he would say, 'Mom you don't need to work.' He would get scratch tickets and if he won anything, he would give it to mom, $50 in my pocket. He never drank for 24 years. Never smoked."
He never showed a violent streak, she said, making the accusations against him so shocking.
After Bampumim moved out, Maria Luisa picked up reports of him acting strangely.
One of Bampumim's close friends told her he ran into him at a bank on Adams Street in Boston.
"He [the friend] said, 'What's up? Hey, brother,' and Bampumim said, 'I think you are confused,' " Maria Luisa said. "He says, 'No, you're my brother, Luisa's son,' and he said, 'No, you're confused,' and left."
Lived in a shelter
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.
"I wasn't sure if he didn't want to see me for the second time or if he had moved out," she said.
Maria Luisa was so out of touch with Bampumim that she didn't know he'd already been in trouble with the law.
He passed notes demanding money at a bank in 2014 and 2016, Suffolk County District Attorney's Office spokesman Jake Wark said. Bampumim didn't use a weapon in either incident. He pleaded guilty to both crimes and was sentenced to nine months in jail, plus probation, Wark said.
That crime seems out-of-character for the Bampumim she raised, Maria Luisa said.
"The thing about stealing, it's the first time I heard that," she said. "Stealing, I never, in my life. ..."
2 counts of murder
Investigators haven't provided much information about Bampumim's life in Boston.
The District Attorney's Office said he was in the United States legally with a green card obtained in 2010.
He held a security job from October 2015 to April 2016 at a building adjacent to the condo complex where Field and Bolanos lived, according to a law enforcement source.
There's no evidence he knew the victims. And nobody has said how he got up to their two-bedroom, two-bath penthouse in a building that has a 24/7 concierge and other security features
Authorities said police went to the building last Friday after Richard Field texted a friend that there was a man with a gun in the building. Inside the penthouse, officers encountered a man wearing gloves and dark clothing in the hallway and shot him in the left hand, abdomen and leg, thinking he had pointed pistol at them, authorities said.
Police found a realistic looking replica of a .357-caliber Magnum at the scene, law enforcement sources said. Teixeira was taken into custody after what police called "a violent struggle."
Field and Lina Bolanos had their hands bound and their throats slit, a law enforcement source briefed on the investigation told CNN. Blood was splattered around the apartment and photos of Field and Bolanos had been cut up, two law enforcement officials told the Boston Globe.
Police also found a black backpack full of jewelry, presumably belonging to Bolanos.
Bampumim Teixeira was charged with two counts of murder. Court hearings have been held while he lay in his hospital bed and he has said little. He has pleaded not guilty. Steve Sack, Teixeira's lawyer, declined to comment to CNN, citing attorney-client privilege.
A probable cause hearing is scheduled for June 8. Authorities have not publicly offered a motive, as the investigation continues.
'You would feel destroyed'
Maria Luisa Teixeira, 68, still lives in Boston, in a tidy apartment decorated with photos of her late husband and other relatives, including Bampumim.
She's worried about how his arrest is affecting other family members, like his foster sister in London, Sandra Almeida.
"She cries, she's gone three days without food, asking me if all she's seeing around is true," Maria Luisa said.
Meanwhile, Maria Luisa tries to figure out what happened to the loving young man she helped raise. She knows there's a good chance she'll never see him in person.
"If you raised someone ... how would you feel?" she said. "You would feel destroyed, it would kill you, like you're nobody. Because I wanted to see this little one, who is in this state today, as the one I knew and raised."