The Lieutenant and Sergeant were played by real-life brothers Frank Campanella and Joseph Campanella. This was Frank's sole series appearance, while Joseph appeared three times, each time as a different Lieutenant.
The scenario of a barricaded armed suspect in modern times would be handled by a Special Weapons and Tactics (SWAT) team, but those did not exist until the 60's. The acronym was first used in Philadelphia circa 1964 to deal with bank robberies. The Los Angeles Police Department advanced the concept as well.
A precursor for recycled characters ala Law & Order (1990): Second series appearance of Barbara Barrie within a short period of rime. She previously appeared in The Red Clown (1957) just two months earlier. Casey had contact with her character both times.
Casey again breaks the fourth wall at the end by talking directly to the camera instead of using her normal voice over.
Casey when talking about the gun she is carrying describes it as a "...magnum pistol, the most powerful handgun in the world..." That is essentially the same line used by Clint Eastwood some 13 years later in Dirty Harry (1971) when he describes his 44 magnum handgun as "...a .44 Magnum, the most powerful handgun in the world..." The 44 magnum was first sold by Smith and Wesson in January 1956, just 2 years earlier.