According to that tenant, the male shot and killed the female in the hallway of the duplex.

Single female.  

A few years ago I had a single female tenant and she had called to ask if we came in her house. 

It would be the real estate equivalent of blind orchestra auditions Orchestrating Impartiality: The Impact of “Blind” Auditions on Female Musicians | Gender Action Portal (harvard.edu).

@Anthony Angotti I do not believe so, even the one i mentioned - if you read the link i posted, even the provision i mention disappears if you own more than 3 rental properties. so if my daughter was living in one and i rented the rest of the rooms ( which i did ) i could specify that the other renters are female, once i own a 4th rental property, that wouldn't matter and i would have no say ( read page 3 and 4 section (b) and what i mention about over 3 houses is in section (b)(1). renting out rooms is same as renting out rooms in a B&B, you can not discriminate then and you can not discriminate if it is a student rental.

And I notice from your picture, you are young, and female. 

I am a female, general contractor, that builds spec new construction.

For males and females between 25-34 college graduates make 1.75 times more than high school graduates.Ex.

I see people routinely trying to rent a room in their place or attached apartments to only females.

Get the boyfriend to release any rights in writing and obtain a new lease with the female.