Both men had to go to the hospital. BART officials say they have nothing to hide as they investigate this case.
"We are keenly aware of what YouTube brings to the public we want to assure the public we want to ensure the public we are moving forward we are not waiting we are investigating to the fullest extent," said Daniel Hartwig with the BART Police.
BART's police force has been under intense scrutiny since an officer shot an unarmed passenger to death on New Year's Day.
Michael Gibson's sister said her brother has been diagnosed with bi-polar disorder and schizophrenia and is on medication. She said she is outraged at BART for what this video shows.