'So heartsick,' the actress wrote on Twitter after learning of the Hollywood icon's death.
Debra Messing is mourning the loss of her TV mom, Debbie Reynolds.
The 84-year-old actress was hospitalized on Wednesday after suffering a possible stroke at her family's compound in Beverly Hills, California. She died later that day at Cedars-Sinai Medical Center, one day after the death of her daughter, Carrie Fisher.
"So heartsick," Messing wrote on Twitter on Wednesday. "Debbie went to be with Carrie. It's such a devastating 1,2 punch."
"She was my 'mom' for years & I loved her dearly. A legend," she continued.
Messing and Reynolds had a dynamic friendship both in front of and behind the camera, creating TV magic as the hilarious mother-daughter duo on the hit NBC show Will & Grace.
Sean Hayes and Eric McCormack, who also starred on the show, also paid tribute to the iconic star.
"It is beyond astonishing that both @carrieffisher & @DebbieReynolds1 have left this earth," Hayes wrote, along with a photo of Reynolds. "I overwhelmingly adored & admired them both."
"The combination of the loss of @carrieffisher & then her mom @DebbieReynolds1 is too much. I'm really at a loss here... #toomuch16," McCormack wrote on Twitter.
Messing, Hayes and McCormack are reportedly working on a reboot of the Emmy-winning series with co-star Megan Mullally.
Will & Grace creators Max Mutchnick and David Kohn reunited the group in September for a hilarious election-themed skit.
McCormack and Messing returned as Will Truman and Grace Adler, along with Mullally reprising her role of the outspoken Karen Walker, and Hayes as Will’s lovable neighbor, Jack McFarland.
The mini-episode snagged more than six million views on YouTube, prompting NBC execs to reportedly consider a series rebirth.
EXCLUSIVE: Megan Mullally Talks 'Will & Grace' Revival
As for when we'll see a reboot, that's still TBD, but Mullally says she hopes it will happen.
"I think that it would be a lot of fun to do," she told ET earlier this month. "I don't know -- it's nothing official yet, but we're hoping," adding we'll have to ask NBC or Netflix "real nice."