A deranged man fatally stabbed his mother inside her Brooklyn home yesterday, police sources said.

The suspect, who has not been identified, was arguing with Alfonette Scarder, 47, inside her Flatbush apartment on St. Paul’s Place at about 11:00 p.m. Wednesday

when he viciously stabbed her, police sources said. EMS responded and rushed Scarder to Kings County Hospital where she later died.

The assailant, who suffers from bipolar disorder, was arrested at the scene, police sources said. He has not yet been charged.