Jonathan Dos Santos’s family moved into the three-decker on Fuller Street with hope that it would be safer than their old neighborhood. The 16-year-old decorated his room with mementos he was proud of: his certificate of graduation from fifth grade, a Boston neighborhood soccer league plaque, football trophies, a silver and blue 5K medal on a bright yellow ribbon.
But about two months ago, the teenager came to his basketball coach with a problem: People were hassling him, trying to get him to join a gang, the youth had said. He didn’t want to. But he was scared to go to school because he was afraid they would be looking for him at the train station.
On Wednesday night, two young men waited with guns drawn for Dos Santos to come riding his bicycle down Fuller Street in Dorchester, according to an official briefed on the investigation. When the teenager pedaled past, they opened fire, killing him.
“This was an ambush,” said the law enforcement official.
Paris Cherry, the coach in whom Jonathan Dos Santos confided, said the teenager was a great kid who flourished with positive attention from coaches and mentors. But he lived in a violent world, and some of his friends were involved with gangs, Cherry said.
“Unfortunately for these kids, living in an urban environment, by default some of your friends and classmates are involved,” he said. “You’re taught not to leave the environment. There are so many forces that always pull you back.”
On Thursday morning, Laura Dos Santos stood in her son’s room among his treasures and wept.
Family and friends said her son was a quiet boy who dreamed of playing sports in college, just filled out an application for a summer job, and fiercely protected his little sister, 9-year-old Jennifer. He always told anybody who gave her a hard time to “back off.”
“Whenever I get scared, he just hugs me,’’ said Jennifer. “I don’t really say anything. I just hug him.”
She said she saw him Wednesday afternoon, when they came home from school. Her brother went to McKinley Preparatory High School in the Fenway. Jennifer went to do her homework, and Jonathan sat down with his friends. She never said goodbye.
Dos Santos’s father, Joao, said his son was going to visit his aunt and uncle when he was killed. The last conversation they had was Tuesday night, when he told the youth to “be careful.”
“He didn’t really respond to me, because he was used to me giving him that talk,” said Joao Dos Santos.
Jonathan Dos Santos bore a striking resemblance to his father: the same slight build and delicate features. And though the teen was born in the United States, he loved the traditional Cape Verdean cuisine and music his parents grew up with.
“I miss him,” said his father. “He was my friend, too.”
Witnesses said they heard five shots at about 8 p.m. Wednesday.
One resident, a 52-year-old man who stepped out onto his porch to have a cigarette, said he saw two people chasing the teenager as he rode his bike down the street.
“They started shooting at him. They were coming up from behind him,’’ said the man, who declined to give his name for fear of retribution. “I think he knew after the second shot that someone was trying to hit him.’’
The teenager crashed his bicycle, one witness said, and as the shooters fled, residents ran to his aid.
The boy’s uncle, Arlindo Lopes Pinto, ran outside to help.
“He looked to me. His eyes were still open,” Pinto said. “I called his name. He didn’t say anything. I took my shirt and covered his eyes. He died in my hands. I just started crying.”
Some said the violence in the neighborhood was inescapable.
“You come out of your house and it’s right next to you,” said Michael Royes, 23, who lives in the area. “You can be who you are but you have to watch your back. And it’s not a choice; we’re just here.”
One of Jonathan Dos Santos’s most special memories was of being far away. In the winter of 2012, after scoring a touchdown for the Dorchester Eagles during a football playoff game, he traveled to Florida with his teammates.
“We were heading down the highway, we got to maybe North Carolina,” said Tony Hurston, coach and director of football operations. “Him and a few other kids, they had never been that far before.”
Every day of that trip, Hurston recalled, Dos Santos thanked his coaches.
Police released detailed descriptions of the two suspects in the shooting, the 11th homicide in the city this year.
One was described as a black male wearing a green hooded sweat shirt with white strings, a white undershirt, blue jeans, and sneakers with yellow soles.
The second suspect was described as a black male wearing a green hooded sweat shirt and light-colored cargo pants with multiple pockets. He had dark sneakers and a baseball cap with cursive writing on the front, a white visor, and a thick white letter on the back of the cap.
Friends said Dos Santos hung out with people “who had problems,” and he got into trouble from time to time.
“I told him, ‘You don’t have to stay out in the streets,’ ” said one friend, Jorge Goncalves, 20.
Dos Santos’s father said he did not know whether his son was involved in any trouble.
His slaying was the second shooting of a youth on a bicycle in Boston within several weeks.
Divan Silva, 7, of Brockton, was shot and wounded while riding his bike on Bowdoin Street in Dorchester on May 24.
On Thursday, his mother, Dijanira De Andrade, visited the Dos Santos home.
She said she has known Jonathan since he was 4 or 5 years old. When she saw his mother, De Andrade said, Laura Dos Santos asked why her son was taken.
“I didn’t know what to say to her,” she said.
De Andrade said she could not sleep Wednesday night thinking about the similarities between the attacks that wounded her son and killed her friend’s oldest child.
“I couldn’t imagine. She just lost her firstborn. Her only boy,” she said.
Police, community leaders, and city officials asked for help solving the killing.
“I’m thinking about me being 16,” Rufus J. Faulk, program director at the Boston TenPoint Coalition, said to a group of community leaders who had gathered at the Twelfth Baptist Church on Thursday to discuss strategies for dealing with crime over the summer.
“Seventeen years later, I’m just trying to think of all the things I would have missed out on if I was killed at 16 — graduating high school, attending college, running for office,” said Faulk. “Or just going out of town and being able to rent a car. Simple things, small things, that this 16-year-old’s not going to be able to do.
“If that’s not a call to arms, I don’t know what is.”
John R. Ellement and Bob Hohler of the Globe Staff contributed to this report.
Evan Allen can be reached at email@example.com.
Correction: An earlier version of this story misspelled Jorge Goncalves’s name and misstated the homicide total in 2015. At the time of the article, there had been 11 homicides in Boston.