Kelly Ripa was just as shocked as the rest of the world when she heard the news that her co-host of four years, Michael Strahan, was leaving "LIVE! With Kelly and Michael" for a fulltime co-hosting gig at "Good Morning America."

After Monday's episode, the bosses at ABC sent out an internal memo that said the former NFL star would leave the show by the end of the summer to start up at "GMA" in September. Ripa was appearently not informed about the decision beforehand and heard about it at the same time that everyone at ABC did.

"She was livid," a source said. "It wasn't pretty."

Strahan has been a correspondent over at "GMA" since 2014 and worked two days a week at the morning news show. The former NFL star replaced Ripa's former co-host, Regis Philbin, in 2012. It was reportedly not his decision to leave "LIVE!," but the executives at ABC who are trying to solve "GMA's" rating problems.

"That was a network decision," the source said, adding that it was a carefully executed plan. "It wasn't an overnight decision and took some time to put it in place."

"He's not the boss," the source continued. "He is an employee of the network."

When the show returned on Wednesday, the day after the announcement, Ripa did not appear on her show and was instead replaced by former "Saturday Night Live" star Ana Gasteyer.

"Good morning, everybody. Kelly is off today," Strahan announced. "I've been in the news lately ... I am leaving this show."

"I'm going to go over to 'GMA' full time," Strahan added, "which is going to happen in September. And it's the same channel!" 

Strahan then went on to address some of the reactions of fans when they learned the news of his departure.

"I was reading some stuff and it was like I died!" he said.

"But I do want to say to all of our viewers out there ... four years ago when I came here I'm sure they were surprised," he said, joking about being the guy with the "gap tooth." 

"I'm always available to guest co-host ... I'm not going anywhere," he reassured fans.

According to ABC News president James Goldston, "Live!" will start looking for a new co-host "when the new season begins in the fall."