An elderly man is dead and police have been taken to hospital with chemical burns following a major operation in Sydney's south-west.
At about 9.55pm last night, police were called to an address in Roselands with reports a man had been stabbed.
Two officers entered the family home and found a 91-year-old man with fatal stab wounds.
As they left the house, the officers suffered chemical burns and were taken to hospital to be treated.
They have since been released.
A 24-year-old man, covered in blood, was arrested at a nearby property.
He is undergoing a medical assessment.
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