More than 30 years ago, a gunman in Arizona was more successful in taking a station hostage:
Here is a description from the person why uploaded the video to YouTube:
"On May 28th 1982, at about 5pm, Joseph Billie Gwin, wanting to prevent World War III, forced his way into KOOL-TV studios in Phoenix, Arizona. After a 4 1/2 hour hostage crisis, KOOL TV finally relented and agreed to go live on the air at about 9:30 pm. Anchor man Bill Close, on the telephone with the police, and with a gun at his belly under the table, read the 20 minute statement live on the air to Phoenix viewers. Gwin monitors with his portable TV to make sure."
And here's a similar incident in Los Angeles a few years later:
If I remember correctly the KNBC one wasn't broadcast, they just did it for show and the guy wasn't monitoring.
The Arizona clip I hadn't heard about, and the fact that he monitored the off-air feed is clever (if that's the right word to use in a situation like this)
Some more information:
The guy entered the building at a few minutes before 8pm. He requested that he would be taken to Studio 8, the studio for the main evening news. The security guy walked along with him to the control room of Studio 10, the studio of the daytime bulletins. In that control room, the crew helped a reporter waiting to go on-air in the main evening news (the reporter was about to go on-air in the main bulletin).
The crew sent the armed guy to the daytime studio, knowing no-one was present there. While the armed guy was waiting there to go on-air (they told him he would go live shortly), the police was called. The building had to be evacuated, since the armed guy handed a letter stating bombs were installed all over.
The evacuation was a major operation, since not only the newsroom had to be evacuated. The Master Control Rooms of NPO1, 2 and 3 (the main channels) is also based there. The transmissions were interrupted for about an hour, at 9pm the parliamentary studio in The Hague finally made it on-air (the main parliamentary presenter was waiting to do a stand-up in the evening bulletin at the houses of parliament, so he had to go back to the nearby studio and the technical dept had to bypass the MCR to broadcast). The Hague showed the video referred to in the first post and the reporter interviewed several colleagues.
At about 10:45, the buildings were released again and broadcasting continued at NPO1 until midnight about the situation.
Later, it was announced the gun he carried was fake. Police reported he made a confession stating he acted all alone.
If I remember correctly the KNBC one wasn't broadcast, they just did it for show and the guy wasn't monitoring.
If you listen to the clip -, it happened live on air but then the director took the decision to take the studio off air (you can see the 'One Moment Please' slide in the gallery footage) but they continued as if it was