That’s up to the agents to articulate and the investigators, prosecutors, judges, and juries to evaluate.
The fact is that law enforcement are able to legally detain people under certain conditions and those conditions do not need to be adjudicated in the moment of detainment. It can come later, and the LEOs can be held responsible if they violated someone’s rights. People on here commenting otherwise either misunderstand the law, or are intentionally providing misinformation to manipulate people and create outrage.