Detroit police are investigating after a pregnant woman allegedly stabbed her mother-in-law to death late Sunday night on the city's west side. 

Police were called on Sunday night around 11:30.

The victim is a 56-year-old woman. She was taken to the hospital but actually died from a heart attack while medics worked on her.

The suspect is her pregnant daughter-in-law who police say is Bipolar. She was also taken to the hospital for a psych evaluation.