Dale Cregan was born on June 6, 1983, in Tameside General Hospital. His parents were Anita Marie Cregan and Paul Cregan, who worked as a tool setter in Manchester. Dale was the second of three children. He had an older brother named Dean and a younger sister. When Dale was young, his father left the family. After that, Paul Cregan remarried a former policewoman who worked for Greater Manchester Police.

Dale went to Littlemoss High School in Droylsden, Greater Manchester. He had some trouble at school and began dealing cannabis. He also developed a strong interest in knives. At one point, Dale lived in Tenerife with his sister for about eighteen months. When he returned to Manchester, he started collecting firearms, and he ended up owning around ten different weapons, including machine guns.

By the time he turned 22, Dale had started dealing cocaine. He claimed to earn around £20,000 a week from his illegal activities. However, he told others that he worked as a plasterer. Cregan became known as 'One Eye' because he was missing his left eye. It is believed he lost the eye in a fight in Thailand, but the exact circumstances are not clear. During his trial, he had to remove his false eye to show police officers that he was not hiding anything.

On 18 September 2012, Dale Cregan killed two police officers, Fiona Bone and Nicola Hughes, in an ambush. The officers were responding to a call about a burglary in the village of Mottram in Longdendale, Greater Manchester. The emergency call was made by Cregan himself, who led the officers into a trap. When the officers arrived at the scene, Cregan opened fire with a Glock pistol, firing 32 shots in just 31 seconds. He also used an M75 hand grenade during the attack. Fiona Bone was killed instantly, while Nicola Hughes was wounded and later died in the hospital.

After the killings, Cregan walked into a police station in Hyde about an hour later. At that time, he was already wanted for the murders of Mark Short and David Short earlier in 2012. Cregan had been on bail after being arrested in June 2012 in connection with Mark Short's murder. He was charged with the murders of the two police officers and the Shorts, along with multiple counts of attempted murder.

Cregan appeared in court for the first time on 21 September 2012. He later faced further legal proceedings, including a plea and case management hearing on 5 November 2012. Although he initially pleaded not guilty to the murders of Hughes and Bone, Cregan changed his plea to guilty in February 2013. Three months later, he also admitted to the murders of David and Mark Short.

The killings were part of a gangland feud between two criminal families in Manchester. The use of hand grenades in these murders marked a significant moment as it was the first time such a weapon was used in a murder in the UK.

On 13 June 2013, Dale Cregan received a life sentence with a whole life order, ensuring that he would never be released from prison. Following his sentencing, he was reported to have gone on a hunger strike and was later moved to a secure hospital. He was returned to a prison in Manchester in 2018, where he continued to be a subject of media attention.

In December 2024, Fiona Bone and Nicola Hughes were posthumously honored with the Elizabeth Emblem for their service.