The woman was identified as Santosh Devi, a resident of Uttam Nagar area of west Delhi, and the alleged assailant as Gidesh Singh, 27.
"Santosh Devi resided on the ground floor of the two-storey building. Early on Saturday morning, Singh was roaming in the area. Finding the house open, he allegedly sneaked into the residence and stabbed the elderly woman on her neck while she was cleaning the room and started searching for valuables," said a senior police officer.
However, failing to find anything, Singh climbed up to the first floor, where Devi's grandson was sleeping with his wife and managed to broke open their almirah.
"The couple woke up and spotted Singh who allegedly threatened them with consequences if they raised an alarm. However, the couple managed to lock him inside the room and alerted the neighbours after informing the police," the officer said.
A police team reached the spot and opened the door to find the accused in an unconscious state with his wrist slit.
"We rushed Santosh Devi and Singh to a nearby hospital where she was declared brought dead and Singh was discharged after treatment. A case was registered and Singh was arrested under relevant sections of the Indian Penal Code," the officer added.
( With inputs from IANS )