The terrorist attacks in Paris sent execs at the major broadcast networks scrambling Friday afternoon and adjusting primetime programming plans in light of the bombings and shootings left more than 100 people dead.

ABC and NBC quickly revamped regularly scheduled 10 p.m. newsmagazines to become live updates on the brazen violence that prompted French president Francois Hollande to put the entire nation on lockdown, complete with closed borders. NBC also opted to air a rerun of its 8 p.m. sitcom “Undateable,” which has been airing in a live format on both coasts this season.

ABC’s “20/20” will be anchored out of New York by David Muir and Elizabeth Vargas. “Dateline” will devote its hour to the attacks, anchored by Lester Holt. “Dateline” will be updated for its West Coast airing.

PHOTOS: Paris Terror Attacks

The horror of the hostage crisis unfolding at a concert venue was magnified by reports swirling on social media that as many as 100 hostages were being executed one by one inside the Bataclan theater. French TV networks were asked by the government to drop their live shots from outside the theater around 6:30 p.m. ET, according to reports from French media, in preparation for police to move on the theater. French media reported that at least 70 hostage had been killed during the two-hour siege in which gunmen reportedly shouted pro-ISIS statements.

Fox issued a notice to affiliates that they had the option of carrying Fox News ongoing coverage of the situation rather than regular programming. ABC, CBS and NBC monitored the situation and scrutinized program lineups for plots and stories that would hit too close to home after today’s events.

CBS opted to stick with tonight’s episode of police drama “Blue Bloods,” which has a B story that focuses on a hostage situation.

In addition to turning “20/20” into a live update on the Paris situation, ABC News said tonight’s edition of “Nightline,” following “Jimmy Kimmel Live” at 12:35 a.m. will be live, anchored by Juju Chang.

Fox News said it would bump its regular lineup of primetime series to stay with the breaking story. Shepard Smith will anchor coverage through 9 p.m. ET, followed from 9-11 p.m. ET by Megyn Kelly.

NBC News said Matt Lauer and Savannah Guthrie will anchor a special edition of “Today” on Saturday morning. CBS News said it would proceed with Saturday’s planned Democratic debate in primetime. “Tonight’s attacks in Paris require important questions for candidates,” Steve Capus, exec producer of “CBS Evening News with Scott Pelley” said in a tweet Friday.

CNN and MSNBC went wall-to-wall with coverage of the Paris attacks since the attacks and hostage situation began to unfold around 4:45 p.m. ET.

The scramble for coverage and commentary in the fast-breaking situation spurred MSNBC to reach out to French journalists from other news orgs and American journalists in Paris.

Laura Haim, the White House correspondent for Canal Plus, offered multiple updates for MSNBC. She also offered key context about the growing ranks of young Islamist radicals in France who express sympathy to terrorist orgs such as ISIS. And she noted that Friday’s attacks come less than a year after France was jolted by the shootings of 12 staffers at the satirical magazine Charlie Hebdo in January.

“Everybody is in shock — complete shock,” Haim said of her colleagues in France.