As a kid growing in America, I was told that the 2nd Khalifa, Mirza Basheer ud Din Mahmud Ahmad was stabbed on a Wednesday while leading prayer at the Masjid Mubarak in Rabwah (March 10th, 1954, see Rashid Ahmad). In 1957, Jalal ud Din Shams confirmed this story via a speech at the 1957 Jalsa at Rabwah, which was later converted to a book, “The Noble Son” by Jalal ud Din Shams, 1957, see page 95.
The story also exists in 1966 (See Truth Prevails, aka Ghalb-e-Haq). In 1965, the Lahori-Ahmadi’s wrote about the Khalifa while he was on his deathbed in a disrespectful manner, in this book, they asserted that the Khalifa had went crazy as per the wrath of Allah since he claimed to be the Musleh Maud in 1944. They posted many references from the Al-Fazl which spoke of the Khalifa’s miserable condition. However, they didn’t mention any stabbing incident.
As an additional piece of evidence, we cite SE Brush and his academic work of 1955 wherein he visited Qadian (in 1953 and early 1954) and even spoke to the Khalifa. He didn’t mention anything about a stabbing, he might have left before March 1954, when the stabbing happened. Moreover in 1955, the Khalifa travelled to London for the second time in his life and never mentioned any incident of stabbing. Further, Rashid Ahmad, the first ever Qadiani-Ahmadi murrabi claimed that he was in Rabwah in 1954 when the stabbing happened. He claims that he was missing from the masjid on the day when the Khalifa was stabbed. He claims that some boy (allegedly, a non-Ahmadi Muslim from Chiniot) slipped into his spot in the first row behind the Khalifa.