LOWELL — Heartbroken and confused neighbors, friends, and family members of 17-year-old ­Eddie Gayyean gathered at his family’s home Tuesday with one searing question: How did the studious, outgoing teenager end up dead in the Lowell High School swimming pool?

“We’re just trying to figure out how this whole thing happened,” said Josep Varnie, Gayyean’s uncle, outside Gayyean’s two-story home on Fourth Street.

Gayyean, who had emigrated from ­Liberia just four months ago, had gone to the school earlier in the day to hand in ­paperwork picking his electives for the upcoming academic year, his uncle said.

When the boy’s mother ­returned home from work and could not find him, she called police. Authorities then made the connection between the missing boy and a body found in the pool around 5:30 p.m.

A coach of the New Wave Swim Club discovered ­Gayyean’s body floating in the pool in the ­Raymond E. Riddick Field House, police said. They are reviewing video surveillance footage of the building to determine how Gayyean ­entered the pool area.

It was unclear whether ­Gayyean knew how to swim, his uncle said.

Stephanie Guyotte, spokeswoman for the Middlesex district attorney, said that her ­office is investigating the death with Lowell police and that officials believe it was a drowning.

“It’s obviously a tragedy,” said Mayor Patrick Murphy of Lowell. “We’ll have to see what comes from the investigation, but obviously our thoughts right now are with his family members.”

In April, Gayyean moved to the United States from Liberia with his father and two siblings to join their mother, who had come to this country in 2000.

The death has rocked the ­African community in Lowell. Family members, friends, and acquaintances stopped in at the family’s light green home to show their support throughout the day Tuesday.

“If something happens to an African, we all show up,” Varnie said.

Neighbors described the boy as friendly and outgoing. In just a few months, he had built relationships with many residents of the racially diverse street where his family lived.

“I think everybody on the street knew who Eddie was, not just the African children, all of the children,” said Moses Okononoh, a Fourth Street resident who came to Gayyean’s house Tuesday afternoon.

Another neighbor, Sylvester Osifo, said Gayyean could often be spotted walking on the street and chatting with neighbors.

Osifo, who spent about three hours at Gayyean’s home Tuesday, said he heard about the teenager’s death Monday night and felt he needed to come show his support.

“He was a nice kid, and this is a nice family,” he said.

Varnie said the family has felt uplifted by the show of support from members of the community. Now they are awaiting more details about what led to Gayyean’s death.

“How he got into the pool is a mystery for us,” he said.