Dec. 13 is China’s day for remembering the Nanjing Massacre — but the way some Shanghai basketball fans marked the occasion has landed their team in hot water.

Shanghai Sharks fans allegedly yelled, “Why didn’t your team get murdered during the Nanjing Massacre?” during a match between the Sharks and Nanjing Tongxi Monkey King, a team that comes from the city that saw mass killings of civilians by invading Japanese troops in 1937.

“More than 300,000 soldiers and civilians in Nanjing city were massacred,” the Nanjing team later wrote in a Weibo post describing the fans’ behavior. “Our club hopes the relevant departments will thoroughly investigate this matter!!!”

The Shanghai Sharks — whom Yao Ming once played for — posted an apology Thursday night.