“The Mysteries of Laura” star Debra Messing has apologized for a since-deleted tweet some felt was insensitive to Wednesday’s murder-suicide at UCLA.

Messing, 47, tweeted that she and other advocates against gun violence were asked to post selfies wearing a T-shirt emblazoned “Under the Gun.” She did so alongside TV news coverage of the killings, prompting criticism. “I was so shocked and struck by the horrible IRONY that yet another shooting was occurring as I was participating in this effort,” she wrote, saying she had attempted “to highlight the irony.” She added, “I am heartbroken and embarrassed that many people misconstrued my actions and that I caused offense,” and concluded, “I am so truly sorry.”