“At this time we ask for privacy to grieve and to come to terms with the impossibility of saying goodbye to Bryan.”
The heartbreaking statement was signed off by “His Loving Family”.
Bullock first met Randall - who worked as a model prior to taking up photography - in January 2015, after he was hired to take pictures at her son Louis’ birthday.
The couple went public later on that year, making an appearance together at Jennifer Aniston and Justin Theroux’s wedding.
Bullock - who is mum to Louis, 12, and Laila, 10 - announced last year that she was taking a break from acting in the hopes of spending more time with her partner and children.
She explained: “I just want to be 24/7 with my babies and my family,” adding that she needed to be “in the place that makes [her] happiest”.
There is no known cure for ALS, a neurological disease that develops at different speeds in different patients.
Those who suffer from ALS have a life expectancy between two and five years after symptoms first arise, however 10 per cent of patients live at least 10 years.