A car bombing at Harrods department store in London killed six people, including three policemen, on Dec. 17, 1983. The bomb had been planted by members of the Provisional IRA. An inadequate warning was supposedly sent but the area hadn't been evacuated in time. 

The Malmedy Massacre occured on Dec. 17, 1944, as more than 70 American POWs were gunned down by Waffen-SS troops. This exerpt is from Ryan Little's film "Saints and Soldiers".