Help please

My son is almost 3 years old and we are currently dealing with an issue that he hits me and only me. He won't hit dad, or his sitter. I am certain he learned it from our neighbors kids that are around the same age- when their mom says "no" they hit her. He never did it until he saw them do it. I have tried time-outs, ignoring him, I just don't know what to do anymore-can anyone help me please?

About Danielle
Birth: January 07
On since: Mar 17, 2014
We now have 2 kids, one boy and one girl! The age difference in our kids is the same between me and my older brother!