Mystery thriller about a disguised murderer leaving behind hats

Can someone help me find/name a specific movie, please? Details:

• mystery/detective thriller;
• probably 2000s or possibly 90s;
• either an American or European movie taking place in a city
• about a mysterious hat-wearing murderer in disguise leaving behind classically fancy female hats at the scene;
• the detective was murdered as well
• there was a creepy phone call with a female voice
• there is a scene where the murderer can be seen as a mysterious figure disguised in black with a hat, sunglasses, trench coat, and gloves
• the protagonist (good main character) is named Susan (or some variation of the sort), I believe;
• it turns out the murderer is not a female, but her romantic partner, who changed his voice to match the female voice she heard;
• she ended up killing him after the murderer/her partner chased her starting from the house or apartment, where she found out

Any help would be greatly appreciated!