The mother-in-law of a 33-year-old woman battling an aggressive form of leukemia organized a surprise flash mob for her on the roof of a parking garage overlooking her hospital room.

“Everybody who wanted to see her and send her their support, we decided to gather here and wave to her and do the best we could that way,” Tracy Todd’s mother-in-law, Michele Thomas, told KSDK-TV.  

“Team Tracy” gathered on a roof near Tracy’s Barnes-Jewish Hospital room Sunday with signs and shirts showing messages of support.

“And I think it worked because she seems happy,” Thomas told KSDK-TV. Tracy’s husband, Kevin, wrote on the family’s blog that the support has been “indescribable.”

Tracy, who lives in St. Louis, Missouri, was diagnosed with acute lymphoblastic leukemia on Jan. 3, according to a post on the family’s blog.

Tracy is being treated with two types of chemotherapy, and cannot have many visitors, Thomas told the news station.