Investigators discovered a note at the scene of a grisly murder-suicide where a Viagra chemist from Brooklyn was shot dead apparently by her husband.

Elsie Jones, 39, who helped to produce the famous blue pill, and her husband, Peter Jones, 53, were found shot to death in bed at their Canarsie residence on St. Jude Place at about 11:35 a.m. Friday, cops said.

It was not immediately clear what the note said.