Following the attempted assassination on his life on 19 February 1937, governor Rodolfo Graziani believed the monastery's monks and novices were involved in this attack, and unwilling to wait for the results of the official investigation, ordered Italian colonialists to massacre the inhabitants of this monastery. On 21 May of that year, 297 monks and 23 laymen were killed. Overall, between 1,700 and 2,100 civilians were slaughtered in two mass executions on 21 May and 26 May. Although when Buxton visited Debre Libanos in the mid-1940s, he found the remains of these victims were plainly visible ("Here were innumerable bones and skulls – bones in bags and bones in boxes, bones lying in confused heaps, awaiting burial"); a cross-shaped tomb was afterwards built to contain their remains, which stands next to the parking lot.