A New York Times investigation found that credit cards were used to fund at least eight of the past decade’s 13 mass shootings with at least 10 casualties. The eight mass shootings took the lives of 217 people. If someone had been looking for red flags, they would have found plenty, law enforcement experts say.

In the eight months before Omar Mateen killed 49 people and wounded 53 more at the Pulse nightclub in Orlando, he opened six new credit card accounts. Twelve days before the shooting in June 2016, he began a $26,532 spending spree on guns, thousands of rounds of ammunition and a $7,500 ring for his wife. His average spending before that, on his only credit card, had been $1,500 a month.

Two days before the shooting in Orlando, Mateen googled “Credit card unusual spending,” “Credit card reports all three bureaus,” and “Why banks stop your purchases.” The New York Times writes, “He needn’t have worried. None of the banks, credit-card network operators or payment processors alerted law enforcement officials about the purchases he thought were so suspicious.”

Banks are already capable of analyzing transaction data to protect their customers from fraudulent purchases and to detect money laundering or funding of terrorist organizations. The suggestion is that banks could also add information about gun sales to their infrastructure to help the government investigate — and possibly even prevent — mass shootings.