David Mathias III, 59, was stabbed by his girlfriend of 10 years at his home in the 6200 block of Foster Drive in the Morrisville section of the township, police said.
It happened around 4 a.m. on Sept. 12.
Police say Mathias had been suffering mental health issues, and had a severe episode that morning.
Mathias attacked his 45-year-old girlfriend with a knife, police say. She managed to get the knife away and fatally stab him.
His girlfriend suffered 'significant defensive wounds' to her hands, police said, and had to undergo surgery and physical therapy.
Police say Mathias had been recently been receiving treatment for his mental health issues.
In a statement, Falls Township police said, "This was a very tragic case which, at its conclusion, determined that a very well-respected, peaceful and generous man suffered from a rapid descent into a major mental health problem very late in life which caused the fateful encounter with the victim."