A 24-year-old man who died after being found seriously injured at a house had been stabbed, police said.
Darren Leonard was discovered at 11.30pm on Wednesday after police were called to reports of a disturbance at an address in the Northfield area of Hatfield, Hertfordshire.
Ambulance crews were also called and Mr Leonard was taken to Lister Hospital in Stevenage, but died shortly afterwards.
A spokeswoman for Hertfordshire Police said a post-mortem examination revealed he died as a result of stab wounds.
Detective Chief Inspector Martin Brunning, from the Bedfordshire, Cambridgeshire and Hertfordshire Major Crime Unit, said: “We are determined to catch the people who killed Darren and will leave no stone unturned in order to find them.”
Police have been carrying out house-to-house inquiries in the Northfield area and monitoring CCTV footage from cameras situated in the area.