Bertha Lopez was dropping off her granddaughter at school and found it hard to contain her anger after finding out Hernandez may have raped a student who is a relative.
"I can't understand people like that, really, really I am very upset about that," she said.
A few hours later, she and a few others handed out wanted posters with his picture around the Castro and Mission districts.
The incident occurred Thursday at Sanchez Elementary. Hernandez came to the school with lunch for the second-grader. School officials said it was something he did on several occasions.
"The family was aware of his being a part of the school community, coming and bringing the child lunch, and participating in the life of the school and the child," said Gentle Blythe with the San Francisco School District.
But Thursday a teacher's aide told police things did not seem right.
"One of the things she articulated was the behavior was overly affectionate," said San Francisco Police Lt. Mikail Ali.
When she noticed the girl was missing from the schoolyard, the teacher's aide went looking for the 8-year-old. Police say the teacher found them in a stairwell.
Investigators say a surveillance camera captured the sexual acts. Police described the evidence as "overwhelming." They believe this was not the first incident.
"But perhaps a systematic and over a period of time, abuse, sexual in nature, that is taking place," said Ali.
The report says Hernandez even lived on and off with the family in San Francisco. He also lived in Richmond.
Parents say he was at the school a lot.
"The first time I saw this guy it didn't inspire me a really good feeling," said parent Maria Martinez.
Police do not believe other students were assaulted.
Besides police, U.S. Marshals and the FBI are looking for Hernandez. Also alerted were the Border Patrol and the Mexican authorities.
A letter has been mailed to parents, and the school will open on Monday for those kids who need counseling.
Anyone with information regarding his whereabouts is asked to call police at (415) 575-4444.