[Chimera-users] Mac-Book Pro

I have some students who have mac's, so I tried to download and install chimera on my Mac-Book Pro 17" . I get the following message. I downloaded chimera-1.10.1-mac64.dmg from your site. I am the only user on my computer. Any suggestions? Should I try and downloading it again? Bobby Barnett “Chimera” can’t be opened because the identity of the developer cannot be confirmed.