What's the Name of That Book??? discussion

I have almost no recollection of this book but the only thing I am sure about, is that the main character was a male teenager in high school and that every few days or weeks he would open his locker to find a dead animal (I am pretty sure it was a cat or dog). He said it was the work of time travelers playing a trick on him and I happens all the time. I also vaguely recall him meeting up with either a teenage girl or an attractive older librarian in a secret section of his local library. I also remember a battle of some kind infront of said library. Sorry if the information is a little vague its been atleast 4-6 years or so since I've read it. Thanks for the help!

The Time Hackers by Gary Paulsen ??? Couldn't find anything about a library/museum.

Yes, thank you so much! I've been looking for a long time.