Rivera's mother, Vivian Sanchez, told ABC7 that she believes the alleged shooter was once her son's friend, but the two had a falling out.
"They decided to go outside. About three minutes later, I heard a gunshot and froze. I felt something had happened, and I froze," Sanchez said.
Mrs. Sanchez said the alleged suspect remained at large Sunday night. No charges had been filed in the case.
