Sand. Tea.
Them surrounding the house and getting ready to use a megaphone or such would have been confirming the Intel. You get the ppl out if the house, check it, and then interview them.
In this case, before they can do any of that, guy opens the door and ignores the commands of putting his hands up (which would have shown he had no weapon).
If the next time someone calls in and says "I've shot my mom and am going to kill my sisters if you don't stop me and I'm at xyz place" and they take the time to try to google who might live at the house (spokeo is often inaccurate BTW), see if they can find them on social media, talk to them and see if they've posted about anything, and then determine the threat is real and get to the house only to discover the guy killed everyone and himself guess who's going to get blamed? The cops.
When they call in these false tips they don't give a name. Because then you might be able to look up the person's name.
This is significantly different then a no knock drug warrant in which they've ignored conflicting intell on who lives there or if there are children present.