The victims, a man and a woman, told police the masked man struck them in the head and face.
"She was alone in her bathroom when she was suddenly attacked by an unknown male armed with a hammer," said Capt. John Craig of Northwest Detectives.
It all began late Monday night. Investigators say a 64-year-old woman was bound and robbed inside her home along the 1900 block of Penfield Street in West Oak Lane.
"No doubt it was very traumatizing for the victim. I couldn't imagine what was going through this poor woman's mind," said Capt. Craig.
The victim told police that the masked man struck her in the head and face. She tried to fight back but was robbed of her handgun.
"He disarmed her of a firearm that she had nearby and then tied her up with an extension cord, speaker wiring, and some duct tape. He held her for approximately four hours," said Craig.
The victim's male roommate came home and he was also attacked. The robber took $1,500 in cash.
We spoke to their neighbor about what happened.
"Nobody made any noises, no banging. As far as I know, they tried to get in through the garage. That didn't work, and next thing I know - in the morning - I'm finding out that there was somebody in the house," said Zebalee Thomas Jr.
Police are still looking into how the armed robber got inside since there is no sign of forced entry at the home.
Investigators are looking for the attacker, but have a vague description to go on. He was wearing a black mask.
"The severity and the brazenness, knowing that this individual is armed, makes this a game changer for us. This is obviously very nerve-wracking and hopefully, we can get the individual in custody as soon as possible," said Capt. Craig.
Both victims are stable and recovering at Einstein Hospital.
RELATED: Check the 6abc Neighborhood Safety Tracker