Country music legend Glen Campbell, who was diagnosed with Alzheimer's disease last year, rocked the Grammys on Sunday in the final performance of his career.

The singer received a standing ovation during his performance of Rhinestone Cowboy, at which point two Grammy guests were spotted sitting and texting on their phones. The incident attracted grave criticism from celebrities in the audience, who took to their Twitter account to vent.

Tweeting from audience rather than standing and applauding a living legend like Glen Campbell is simply rude, tweeted Kristen Chenoweth upon spotting the women.

Awful Women who were texting during Glen Campbell's ovation should publicly apologize, tweeted Todd Barry.

The women have not been identified but a numerologist who claims to be one of the women, sent out a message apologizing. She claimed she was tweeting about her apparent love for the country singer.

Campbell was diagnosed with Alzheimer's disease last June, but he had no problem remembering the lyrics to his song Rhinestone Cowboy, which he performed with The Band Perry and Blake Shelton as a part of a tribute to his musical legacy on Sunday.

Within minutes of hitting the stage, the 75-year-old had the A-list crowd singing and dancing along, including two of his biggest fans, Paul McCartney and guitarist Joe Walsh. Campbell held his microphone out to the audience as they sang along to his flawless performance.

Thank y'all so much, Campbell yelled over the hail of cheers that followed the tribute. The country music veteran is a five-time Grammy winner. He has suffered from short-term memory loss for years and went public with his Alzheimer's diagnosis last year, ahead of his final farewell tour.

Campbell first started out as a guitarist in the Beach Boys, before rising to fame with his hits, Wichita Lineman and Rhinestone Cowboy, in the 1960's. He also hosted his own variety show, Glen Campbell Goodtime Hour, between 1962 and 1972.

Here's his Tribute performance at the Grammys, in case you missed it: