Police launched a murder investigation after a man in his 20s died from serious injuries suffered in an assault in Gainsborough.
As previously reported, a second man was arrested in connection with the assault which prompted an armed police response.
A man was sent to hospital for treatment after being left with serious injuries in an incident on Scampton Way in Gainsborough at 10.43pm on Wednesday, March 27.
Armed police were deployed to Ropery Road in Gainsborough during the afternoon of Thursday, March 28.
A 21-year-old local man was arrested in connection with the incident before being released on police bail pending enquiries.
A second man, aged 22, was arrested on March 31 and remains in police custody.
Police said on April 2 that the force is now treating this incident as a murder investigation.
Anyone with information or who witnessed the incident should contact police on 101 quoting reference number 436 of March 27.
It can also be reported through the independent charity Crimestoppers on 0800 555 111.