The accused has been arrested on charges of murder.
An Army jawan allegedly killed the fiance of his former girlfriend, while severely injuring her at a bus stand in Punjab's Rupnagar area, police said on Monday.
The incident took place on Sunday when 27-year-old fiance, identified as Neeraj Kumar, and 26-year-old Shivani Sharma, were going to Nalagarh from their hometown of Una in Himachal Pradesh
Kamal Dev, 27, also from Una, and posted in Jodhpur, was allegedly following and harassing the couple in a bus on their way to Nalagarh, police said.
Dev - who also got down at the bus stand in Rupnagar, attacked Mr Kumar with a sharp-edged weapon. Ms Sharma suffered serious injuries trying to save her fiance, Rupnagar Deputy Superintendent Randhir Singh said.
Mr Kumar, who received serious injuries around his neck, was declared brought dead at the local hospital and Ms Sharma was referred to Chandigarh's Postgraduate Institute of Medical Education and Research, police said.
An angry mob caught hold of the accused, beat him and handed him over to police. A case of murder has been registered against the accused, the police added.
Ms Sharma and the accused were in a relationship earlier but his parents were opposed to it, police said. Later, she got engaged to Mr Kumar and they were supposed to get married in August.