Apology for Unjust Behavior

Dear ___,

I have recently discovered that I've made a huge mistake regarding the incident that occurred between the two of us a while back. I understand now how curtly I spoke to you and how unfairly I treated you only to find out later that it was to no fault of yours.

My actions were unwarranted and unjust. The only beneficial outcome of this unpleasant ordeal is that I have learned a valuable lesson. From now on I will conduct more thorough investigations before I go flying off the handle and wrongly accusing people.

I realize that this may cause a temporary ill-feeling, which I do understand, but at the same time I hope that we are able to remind ourselves of the saying "let bygones, be bygones".

Please accept my sincerest apologies for the inexcusable way I behaved towards you, I genuinely regret it.

Sincerely,