Nisa Mickens and Kayla Cuevas were inseparable since before they could walk, relatives said. The teenage best friends spent holidays together, went to summer camp together and were on the same basketball team.

They may have died together, too.

The badly beaten and cut bodies of both girls were discovered in their suburban neighborhood early this week.

Mickens was found first, lying dead on a residential, tree-lined street in Brentwood at 8:30 p.m. Tuesday, a day before her 16th birthday.

After a day of searching, Cuevas, 16, was discovered along a fence in the wooded backyard of a nearby home. She lived a block away.

As their families struggle for answers about who would kill the aspiring athletes, police said they suspect the killings were committed by gang members, though why anyone would have targeted the girls is unclear.

Kayla's mother, Evelyn Cuevas, said she just wants her daughter's killer captured.

"She was trying to keep focused, but this nonsense that is out here, it's hard for kids," Cuevas said, tears streaming down her face Thursday as she visited the place where her daughter's body was discovered. "They get bullied if they don't participate. They beat them up, they kill them."

Both girls had recently started the school year at Brentwood High School.

Brentwood, a densely populated suburb of 61,000 people about 40 miles (64 kilometers) east of Manhattan, has struggled with an uptick in gang activity. Suffolk County Police Commissioner Tim Sini declined to say if either girl had a connection to a gang.

On Thursday, friends and relatives gathered near the scene of the attack. Blood still stained the ground as mourners left candles, balloons and cards.

Nisa's grandfather, Robert Mickens Sr., placed a basketball next to the makeshift memorial — a tribute he said was fitting for a teen who loved sports and sneakers. A group of about 50 gathered later in the evening for a prayer vigil.

A larger gathering was planned Friday evening in the stadium at Brentwood High.

Relatives said the girls had a natural chemistry.

"If you see Nisa, you see Kayla," Nisa's mother, Elizabeth Alvarado said. "Those girls mean everything to us. We saw them growing up. We ate at the same plate. We encouraged each other."

Investigators have released few details about how the girls died.

Mickens' father, Rob Mickens, said he dropped his daughter off at Kayla's home just before 7 p.m. Tuesday. She sent him a text message at around 8 p.m. asking him to pick her up at 10:30 p.m., but when he arrived she wasn't there.

He said he didn't learn his daughter had been found dead until later in the evening, when he flagged down a police officer and asked for help.

"My daughter was a very caring girl, affected a lot of lives that I didn't even know," he said. "Kayla, also another great girl, but very misunderstood. But she was a good girl."

Both girls suffered significant injuries to the head and face, according to police. Sini, a former homicide prosecutor, called the injuries some of the worst he'd ever seen.

He declined to say why investigators believed the killings were gang-related.