Water leaking into trunk appears to be coming from back window

I have a 2017 Prius 4. I found water in the trunk so I had a friend spray the hatch with a hose while I sat inside the back. The water appears to be coming in though the back window which is under the spoiler. I can see it running out from under that plastic bar on the inside that sits between the upper and lower glass. Does anyone know how I can get the spoiler off so that I can seal it up? Or is there a better method to fix the leak? I am having trouble finding much in the way of instructional videos online. Thanks!