First, Charles is the one who called the police.

Second, when the police arrived, the female and two males were still outside his house. Either they were there to exact revenge on Charles or they were there to finish whatever nefarious business they were up to in the first place.

My guess is, they were surprised by the arrival of the police. Had they know the police was coming, I think they would have been long gone.

Third, it's entirely plausible that the three outside the house, who had first contact with the police, quickly concocted the assault story to cover their own actions.

Now before everybody goes crazy, I'm not arguing that Charles is a choirboy or discussing whether he should or should not be admitted to BYU (that's BYU's decision). I'm just discussing certain particulars of the case I found a bit odd.