John Singleton died of a stroke ... according to his death certificate, but there's a new detail that was kept secret ... until now.
The certificate -- obtained by TMZ -- lists the cause of death as acute ischemic stroke, intracerebral hemorrhage and hypertension. Singleton's date and time of death was April 28 at 3:30 PM ... a day earlier than when his family made the announcement John had passed.
As we reported ... the famed director died Monday at Cedars-Sinai Medical Center in L.A. after being taken off life support following a massive stroke.
The "Boyz n the Hood" director had been in a coma in ICU after suffering the stroke April 17 while in the hospital. He had checked himself in after returning from Costa Rica and experiencing problems with his legs.
John's death sparked waves of reactions from celebs ... Ice Cube, who starred "Boyz n the Hood," gave us an emotional statement on Singleton's passing. Michael Blackson told our photog he was devastated by John's loss, because they were like brothers. Barack Obama remembered him as a trailblazer who told stories Hollywood tried to ignore.
Singleton was only 24 when he directed "Boyz n the Hood" and became the first African American nominated for an Academy Award for Best Director. His decorated career spanned nearly three decades, directing 9 films and scores of episodes on hit TV shows.