Awaiting a response from the accused
I don't understand how alt+tabbing would cause you to pull out your weapon and the fact that you attempted to move away from Dan whilst he was cuffing you to go towards your clan member.
Concluded and denied,
For some weird reason, GMod sets changing your last weapon as alt by default. I'd advise that anyone who gets that to change it so that situations like this don't happen in the future.