I have a red target in the middle of my screen

Not sure what I did to cause this but a red target has shown up in the middle of my screen. It must be some sort of overlay because when I took a screen grab it didn't show up so I had to take a pic with my phone. It looks like this:

I have tried rebooting to no avail. Checked through the accessibility features and didn't see anything that looked obvious. I cycled through the menus on my monitor looking for anything but didn't see any likely candidates. I have a Mac Pro (Mid 2010), 2 x 2.4 GHz Quad-Core Intel Xeon with an ATI Radeon HD 5770 graphics card and an ASUS VG248 display. Any ideas?