✔ 最佳答案
Call the police and follow their instructions. I'd stay there and wait for the police to show up, staying on the phone is safe because there's "someone with you" and if you see anyone you can relay that information to the dispatcher, further helping the case. Hopefully you can at least get in a good description before the crazy guy stabs you to death and then they have audio recording and more proof for the trial.
Seriously though, he'd call the police. Taking it is tampering with evidence and not helping.