NBC Bay Area talked to two girls who say they witnessed inappropriate behavior between Walker and a few girls back in 2008. Allison Hancock and Ashley Barone say Walker was not their nanny, but he was a nanny to one of their friends a few years ago. They say their friend is not one of the victims. Hancock and and Barone say they felt uncomfortable when they went to their friend's home where Walker was babysitting four girls.
"Some are 10, 11. Very capable of changing themselves. So he was in there helping them take off their shirts, put on the dresses and helping them change, I thought it was gross. It was not necessary," Hancock said.
Barone says she saw Walker kissing the girls.
"On the lips, on the necks, on the ears...just like not the way like a grown man should be kissing. He shouldn't even be kissing any of the girls he's nannying at all", Barone said.
Campbell police arrested Walker after one of the victims came forward.
Seven more alleged victims contacted detectives soon after.
Investigators say Walker cared for numerous children either at his home or at child care centers since 2002.
"The children who reported this were obviously strong and did the right thing. We really are encouraging any other children or families who might have information regarding this investigation or other instances to come forward", Campbell Police Sgt. Gary Berg said.