Hello Darkskelly!
I've spoken with both you can Callum about this situation and I've decided to deny your report. As shown in your video you heard shots then watched Callum shooting at someone. You then instantly started shooting at him and kosing him. As you didn't give him any time to identify the body, you joined the gunfight which is against the rules, therefore you were punished. For all you know, Callum could have just killed a traitor, and before he could check the body, you started gunning him down.
In the future, you must give them time to identify the body, if they do not, you may kill them. If they do and it's an innocent, you should ask them why they killed the innocent, if you have enough evidence to not believe their reason, or they do not answer you, then you may kill them.
One thing I did mention to Callum is that he probably should have taken the time to open a chat and explain why you were in the wrong, instead of just instantly punishing you, especially seeing as he was handling his own report. In the future, he will try to make the reasons for punishments clearer in situations like this.