Red flag laws lend themselves to serious abuse, and I don't trust them to either be designed or used in good faith.
However, I would note that whenever a mediagenic mass-shooting happens, in deflecting from gun control many folks on "our side" tend to point to the (inevitable) lengthy history of complaints about often sub-criminal, or mildly-criminal behavior on the part of the shooter and say
"Well, look at how obviously crazy that person was, why didn't the cops do something before he snapped?" I've seen the argument more times than I can count on APS and have probably made it myself. It seems to me that proponents of that position are asking for some sort of red flag laws.
That said, I don't pretend to have any answers. If government could be trusted - both now and in perpetuity - then one might put a lot of possible solutions on the table. But the government absolutely
cannot be trusted.