On June 13, 1901, Ada Maria Redpath and her son Jocelyn Clifford were found shot to death in their home. What exactly happened between the two of them is something we will likely never understand.
Research:

Robert Moses and the Shaping of New York, Part 2
42:12

Robert Moses and the Shaping of New York, Part 1
41:59

SYMHC Classics: Eradication of Smallpox
43:25