There’s actually quite an extensive process. Whether it is constitutionally adequate due process or not will ultimately have to be determined by the courts.
Generally speaking, I have no issue with some sort of “red flag” law, but I would always place the burden on the authorities to prove that the seizure and continuing possession of the firearms is necessary. The owner would never have to prove anything to get them back.
This.
The suspect allegedly committed a crime by calling police and threatening to kill his wife who wasn't home at the time. The family reported his actions and expressed their concerns to investigators who felt there was enough evidence to get an arrest warrant issued and presumably a search warrant. The subsequent investigation of the home revealed what could easily be deemed a threat and the firearms were taken into police custody as evidence. So far I don't see any issue with that.
Now he'll have the opportunity to go before a judge to face criminal charges and potentially questions or evaluation of his mental fitness. I'm not an attorney, but it seems to me that everything up to now is fairly standard. The firearms weren't seized based soley on a tip from family, but rather as the result of the suspect's actions.
If he's ultimately judged mentally competent and isn't convicted of a felony that he should get his guns back. If events play out that way and the state holds onto them anyway, then there might be a valid reason to get upset.