New details emerge about alleged shooting plot from teen girls targeting SoCal high school

CORONA, Calif. -- Students arriving at Corona High School Wednesday expressed shock after learning that two 15-year-old girls had been arrested for allegedly plotting a shooting on the campus.

According to the FBI, the investigation began Oct. 6 after the agency spotted social media chatter about a possible threat. Authorities arrested one of the girls, who was a student at Corona High School.

MORE: 2 teen girls arrested in alleged shooting plot targeting Southern California high school

Investigators later arrested a second 15-year-old girl who attends Norco High School and who the FBI said was also involved in the alleged plot.

The FBI said the two girls had researched school shootings online and discussed how they could carry out an attack and obtain weapons, although no weapons were ever found.

Speaking with ABC LA, Corona Police Lt. Robert Montanez revealed more details about the case.

"I can't really speak to what was in these girls' minds. But yes, there was a list with individuals' names on it, but their target was clearly the school campus," Montanez said.

Montanez was asked about a possible motive.

"Again, I can't speak to what's going in these girls' heads. There is some indication that revenge played some role in this. If that's the case, it's extraordinarily unfortunate that it's got to this point where these girls felt that this was their only avenue to deal with their problems." Montanez said.

Parents reacted with concern as details of the case emerged.

"I think it's really scary. It's really scary that it's two teen girls," parent Jessica Rivera said.

"I don't know what's going on through kids' minds nowadays," parent Adriana Garcia said. "Back when I was in high school, it wasn't really much like that."

Both suspects remain in custody. The two 15-year-old girls are facing charges of conspiracy to commit murder.