A police watchdog is appealing for witnesses to the arrest of a Somerset man who died in custody.
The 25-year-old was arrested in Bath Road, Wells, on 10 June under the Mental Health Act and taken to a cell at Yeovil Police station.
A spokesman from the Independent Police Complaints Commission (IPCC) said officers called an ambulance after they became concerned about his welfare.
The man was pronounced dead at Yeovil District Hospital.
The IPPC spokesman said the local man had been arrested just after 1900 BST, after a number of calls to the police about his behaviour at various locations in Wells.
He said members of the public helped the police detain him and he arrived at the police station at about 2000 BST. The IPCC has the details of three people who assisted in the arrest.
After the ambulance was called, paramedics tried to resuscitate him for 20 minutes, the spokesman said. He was pronounced dead at 2121 BST.
IPCC commissioner Rebecca Marsh said investigators had met the man's family and explained the watchdog's involvement.
A post-mortem examination was carried out on 11 June.
She said: "As this is a death in custody IPCC investigators will carry out an independent investigation into his death and we will prepare a report for the coroner's inquest."
She asked anyone who witnessed the arrest or saw the man earlier in the day to get in touch.
The man, who was seen running in and out of traffic with a St Bernard dog, is described as white, about 5ft 8in and weighing approximately 18 stone (114.3kg).