No further details were released on the suspect.
Students notified officials at Lone Hill Middle School in San Dimas early last week about the threats. One anonymous posting warned the student: "This is your last week. Time's up!!"
Another had a photo of the girl with the caption: "That smile! I can't wait until it's just blood and tears!" The girl was sent home from school until it was deemed safe.
Many students at the school wore blue, the threatened student's favorite color, in her honor while she was out.
From Sandra Endo:
San Dimas Sheriff deputies arrest a juvenile in connection with the Instagram threats which surfaced online last week.
"One juvenile has been detained and booked" said authorities.
The threats targeted a female student at Lone Hill middle school, showing her picture and a number of weapons on social media posts. The instagram threats appeared on various fake accounts and when one account was taken down by the social media site, another would pop up according to school officials.
The case highlights the dangers of social media.
Parent Gina Stanley says,"it's scary, it's concerning, it makes me think the decision to keep my daughter off social media was the right thing to do."
Her daughter, seventh grader Abigail Stanely says, "I feel bad for her (the victim) it's sad."
Lone Hill School officials and deputies say they take cyber bullying very seriously and urge students and parents to take precaution when using social media.
The District Attorney will now determine what charges may be filed in this case.
Deputies say no other students are at risk.