Two men rushed onto the ballroom floor during Monday's live taping of DWTS

The stress of living through Monday night’s protest during the live season 23 premiere of Dancing with the Stars is still weighing on pro dancer Cheryl Burke.

“Cheryl is still shaken,” a source tells PEOPLE. “She can’t believe people can be so hateful and cowardly.”

Burke and her celebrity dance partner Ryan Lochte had just finished their foxtrot and were being critiqued by judge Carrie Ann Inaba on Monday when two men rushed the stage in white T-shirts with a big red circle and line through Lochte’s last name.

Both men were swiftly escorted out of the ballroom by security after host Tom Bergeron announced the ABC reality dance competition would be cutting to an early commercial break.

As many of the other audience members began chanting “Ryan” in support of Lochte, pro dancer Derek Hough rushed out on stage yelling to security to “get them out of here.”

In the moments immediately following the protest, Burke wiped away tears and Lochte looked visibly shaken.

The morning after the terrifying incident, Burke took to Instagram where she admitted that she is “still trying to process everything” that took place Monday evening.

“Thank you to everyone for your concern. I’m still trying to process everything that happened last night. My heart is aching for Ryan and his family. No one deserves that sort of behavior directed at them. We all need to love each other and not be bullies or cowards. Let’s all just be positive for each other. My heartfelt thanks goes out to the security team at Dancing with the Stars. Love you all, Xoxo Cheryl,” the pro dancer posted.

Burke returned to work Tuesday morning for a pro dancer rehearsal and is expected to rehearse with Lochte on Tuesday afternoon.

“[Cheryl believes] DWTS is a positive place for people to grow,” says the source. “Last night didn’t respect that.”