Well, obviously there was a gun, because they were shot by the homeowners.
Also, obviously, their no-knock raid didn’t succeed at it’s intended function, which is to surprise the occupants so you don’t get shot.
The problem was they started by shooting the unarmed dog, instead of pointing the guns at the people and announcing “Police, hands up”.
They lost control of the situation.
Cops had best learn to mind their manners.