Writer and activist Dream Hampton, who worked with Jay Z on his 2010 autobiography Decoded, has revealed some information about the musician on her Twitter account.
Hampton released a series of messages on Twitter that she later deleted on Sunday. However the tweets were screen-shotted and shared on Twitter again.
Hampton said the Jay Z also wrote a check to the Black Lives Matter movement which aims to improve police treatment of African Americans.
Hampton wrote on her twitter account : “I'm going to tweet this and I don't care if Jay gets mad.”
She also said “When we needed money for bail for Baltimore protesters, I asked, hit Jay up, as I had for Ferguson and he wired tens of thousands' of dollars within mins.”
“When BLM [Black Lives Matter] needed infrastructure money for the many chapters that we're growing like beautiful dandelions, Jay Z wrote a huge check.”
Protests began last year after a white police officer shot dead African American teenager Michael Brown in the St. Louis suburb of Ferguson, Missouri.
Major demonstrations took place last month in Baltimore after another African American man, Freddie Gray, died in police custody.
Jay Z performed in New York as an exclusive for Tidal, on Saturday.
During the performance Jay Z paid homage to Brown and Gray.
Last week at a peace concert by Prince in Baltimore, Jay Z and Beyonce met with Brown and Gray's families.
Images of the meetings were posted on social media.
Jay Z, who grew up poor in New York City, was always sensitive about police actions in the USA.
Last year, in December he met New York Governor Andrew Cuomo to press for criminal justice reform.
Jay Z is also known for setting up a fund for the education of the children of Sean Bell, an African American shot dead by police on his wedding day in 2006.