Residents of an Aliamanu cul-de-sac where a 15-year-old boy allegedly attacked and seriously injured his mother and stepfather with a knife say they are shocked such violence could happen in their quiet, tight-knit Navy community.

"We're shocked that it came to this," said Naomi Gee, a neighbor. "They were very, very nice. The boy used to play basketball with his father."

The attack happened about 12:18 a.m. on Saturday at Peterson Court, a Naval housing compound. Police said the boy was arrested on suspicion of one count of first-degree attempted murder and two counts of second-degree attempted murder.

Police also said they believe the victims — a 27-year-old Navy sailor and his 31-year-old wife — will live. The two suffered wounds to their heads, among other injuries.

The couple live in a beige two-story townhouse with blue trim and a tidy yard. In addition to the 15-year-old boy, they have an 18-month-old son, who was sleeping in an upstairs bedroom while the attack was happening, neighbors said.

The toddler has been placed in protective custody, neighbors said.

Megan Sammons, who lives next door to the couple, said she heard screaming and yelling early Saturday morning. When Sammons came outside to see what was going on, she saw the 27-year-old man bleeding and lying on the grass.

The 15-year-old was standing nearby and ran when he saw her, Sammons said.

Sammons called 911. Paramedics found the woman inside the home.

"He was a very quiet kid," Sammons said, adding that the suspect sometimes baby-sat her children. She also said the family was scheduled to leave for California in about a week. The man was getting out of the Navy, she said.

The 15-year-old boy attended Moanalua Middle School and could often be seen playing basketball with a group of teenagers in the community.

Natasia Gascon, who lives in the neighborhood, said the boy and his stepfather had gotten into loud arguments in the past. "We already knew that there was something going on," she said. "The boy was already having problems with his stepfather."

But Christine Hamilton, who also lives in the neighborhood and would often see the victims walking or working outside, said the family appeared happy.

"They were very friendly people," she said. "It is just devastating."

Reach Mary Vorsino at mvorsino@honoluluadvertiser.com.