murderous, murderess, murder us

Murderous or murderous ( one word ) describes something revealing, hiding, or displaying intent to murder--
"We rarely have visitors", said the old crone with a murderous leer.
She shot him a murderous look, but he went right on talking.

Murder us or murder us ( two words, rhymes with murderous ) means the unlawful killing ( murder ) of two or more persons, one of whom is the speaker ( us ) --
Junior's been watching too much TV; he thinks the old woman next door plans to murder us.
He dreamed that our cousin plans to murder us for our inheritance.

Murderess or murderess means a female murderer--
The old murderess had buried several of her victims in the petunia bed.
The trial of the attractive young murderess caused a sensation.

Now that you know that, you can say--
"She doesn't look like a murderess, but that murderous look made me wonder if she plans to murder us."