<not sarcsasm>Police should always clearly and loudly announce their presence when entering an unknown situation.</not sarcsasm>
This is department policy in any good police force!
If the cop had peeked in the window and been shot by a citizen who thought that he was a burglar - which is probable, given that the alarm had been triggered and that the cop was sneaking around, unannounced (as burglars do, and as good law enforcement professional do not - then the citizen would likely have been charged with some crime: homicide, murder or manslaughter, and have his gun taken away forever.
One of the reasons to have a dog on the premises is so that nobody, including the police can be there unannounced.
The police in most areas of the U.S. have become thugs, the good ones quit, because they don't like the direction the department is headed, and new recruits are indoctrinated into the 'Blue Wall/ Code of Silence/ We-are-all-brothers-behind-the-badge/ "There are 2 kinds of people in the world: Cops and perps-and-victims" ' mentality.
I think it's a very telling thing that a search for "Police Riot" on google returns 1,690,000 results, "Riot Police returns 1,790,000.
2,260,000 for "Beaten by Police" 838,000 for "Cops Suck" 708,000 for "Police shoot dog" 260,000 for "unarmed man shot by police"
"Police commmendation" returns 17 results, but 161,000 for "Police fired misconduct".
25,600,000 for "Need more police" 13,900,000 for "Need less police" apparently pro-police-slanted stories are becoming less effective at convincing Citizens that we need more police...
"Police in riot gear" + "nonviolent protest" returns 68... this is a very focused search, yet there are quite a few stories, the meme "Police Riot" meaning a riot-caused or exacerbated by the presence of armed-and-armored police (or soldiers acting in concert with or representing themselves to be Police) has spread like wildfire in recent years.
260,000 for "unarmed man shot by police" 595,000 for "unarmed police" ... seems the public is beginning to wonder whether it is good to employ armed men who consider themselves to be the embodiment of the law or even above the law.
As a security proffessional for several years, I have noticed that people are more willing to do the right thing if they don't feel that they are being coerced, or forced at gunpoint. The Secret Service Presidential Protection detail doesn't arrive on the scene swaggering in body armor and helmets... and also don't tend to provoke the citizenry.
Over-armed and undisciplined police are a danger to themselves, to their community, and a threat to lawful order and discipline.