We're not allowed to trade because it's a misconduct for a staff who's working. They're representing the team. If they allow scamming to staff members, it's a big chance they'd get the item because they are STAFFS, duh...
According to your picture, we need more than that. Yeah we saw the player give tons of shells but we'll need evidence off of PMs, other witnesses (it can be you and others around) and etc.
You said that he'll "quit" the staff team so he doesn't get fired... I'd like to see him say that, maybe if you got a screenshot it's tantamount to say that he's guilty.