I have a firearm and have thought about this. Now I don't like cops in general and I tend to hate them at times. I believe their power over civilians need to be stripped quite a bit.
My purpose in saying that is if I decide to go down that way, I wouldn't feel bad. I may hesitate, but that's it. I couldn't care any less what happens afterwards as long as I'm dead. This is a decent way to go if you can't do it yourself. You can probably shoot once choosing to hit one of them to really make sure they rain down on you, or shoot else where hitting an object instead. Either way, you'll get hit a few times. Just make sure they all draw their pistols first and point your body at them.
Now the problem is there's a chance of surviving the shots. Imagine if you barely survived it. You're disabled, recovering, while also being prepared to either be dropped off in a mental hospital or jail for many years. That's what stopped me from going this route. It would be a last resort if things became even worse for me.