What were you buying form him that costed $400?
Based on this topic, the reason is to btc to usdt exchange. I do not know why this user chose him among the thousands of ways to convert Bitcoin to USDT safely, but there may be another reason.
He did not give us more details, but it is better to avoid dealing with the user until we are sure that he is a scammer.
we did btc to usdt exchange with this user
https://bitcointalk.org/index.php?action=profile;u=3532285same second btc transaction was confirmed he is gone online and not responding to telegram.
Soon i will be uploading whole chat and tx id.
400USD is huge money for me and to my family.
Thanks for reading and be warned