Muska was first detained by security at the Roosevelt Hotel around 2AM. Law enforcement sources tell us Muska was seen spray painting his name on a nearby Coffee Bean.
While security guards waited for LAPD officers to arrive -- Muska demanded the guards let him go, and called them "ni**as" several times ... including one instance in which he said, "Fu** all these ni**as right here."
LAPD eventually showed up and arrested and booked Muska for felony vandalism -- and our sources say Muska had tagging materials on him when he was arrested.
We got shots of Muska's alleged handiwork at the coffee shop -- "Muska"' -- and also at Hollywood's El Capitan Theater ... "Muska kills."
Muska's being held on $20,000 bail.