- NEW: Teen's brother says friend is "devastated"
- Premila Lal was shot and killed by a family friend
- The 18-year-old is remembered as a good student and athlete
- Police call the shooting death "unintended and extremely tragic"
(CNN) -- The combination of a gun and a surprise gone wrong left a beloved 18-year-old track star dead, authorities in Longmont, Colorado, say.
The incident happened Friday when Premila Lal and her 12-year-old cousin decided to play a joke on Nerrek Galley, a close family friend, according to Lal's father.
The Lal family had recently moved, and Galley had been keeping an eye on the recently vacated home.
Lal and her cousin snuck into the house just before 8 p.m. unbeknownst to Galley, who was playing video games with Premila's 15-year-old brother, Pranil.
Galley and Pranil heard a noise and went to check it out, the brother told CNN affiliate KUSA on Sunday.
"We thought maybe there was an intruder in the house and maybe some people knew we moved, and they were coming to check if we got everything so we started clearing the house," Pranil told KUSA.
But the intruder turned out to be Premila, who jumped out of a closet as a harmless joke, according to her family.
"The door opened and she kind of, like, screamed and then Nerrek pulled the trigger," her 12-year-old cousin told KUSA.
Authorities say the family's description of what happened is consistent with their investigation.
"All the witnesses had consistent statements," Commander Jeffrey Satur of the Longmont Police Department told CNN Sunday.