(City News Service)-James Mumper Jr., 19, was arrested about a month after the Nov. 12, 2022, stabbing death of Mateo Castillo, then a senior at Valhalla High School in Rancho San Diego.
Mumper, who was 18 years old at the time of the killing, is set to be sentenced to 12 years in state prison later this year.
Police received a 911 call around 12:45 a.m. on Nov. 12 reporting that someone had been stabbed and was dying in the 900 block of Rigley Street, according to the Chula Vista Police Department.
Castillo was found with at least one stab wound and pronounced dead at the home less than an hour later.
Chula Vista police said that in addition to Castillo’s stabbing, a different 17-year-old boy was stabbed and another was assaulted during their investigation into the party, which was attended by more than 60 people. Mumper was not charged in connection with those incidents.