New Delhi, Sep 28 (IANS): A 25-year-old former tenant has been arrested for killing his landlords -- an elderly couple and their young son -- to avenge a petty issue, police said on Monday.

Mithlesh Mahto was arrested on the intervening night of September 26-27 from his in-laws house in Bihar's Khagaria district.

Police said Mahto killed Chandu Mal, 70, his wife Gullo Devi, 65, and their son Rakesh, 30, on September 23 and fled from Delhi.

Mahto told police that he lived as a tenant on the fourth floor of the victims' flat for three months in north Delhi's Shastri Nagar area.

"Mahto left the flat and went to his home in Bihar 20 days ago, as one day he was beaten up by Rakesh for refusing to give some money demanded by him," Deputy Commissioner of Police Madhur Verma said.

"That day Mahto decided to take revenge. He came back to Delhi on September 22, met Rakesh the next day at the fourth floor of the flat he was residing earlier in and offered him a cold drink laced with sedatives," the official said.

Mahto killed Rakesh when he became unconscious, the official added.

"He then came down to the third floor of the building and slit the throat of the elderly couple when they were sleeping. He also robbed valuables from the house before leaving," Verma added.