The universities have ti exercises their duty of care to their students and their academic and administrative staff as a top priority.
Reputation is down the list of priorities. Besides, there are no direct accussasions against the uni, at least not something we know about.
He is their student plus he is their employee as a TA. Duty of care is on them. When and if (logical AND) he is convicted, then they are free to decide what to do. However, his guilt is far from being proved, he basically has no idea what incrominating evidence they have against him. The step is preemptive for no reason, as noone at the uni is under imediate danger (he is in custody).