MILWAUKEE (CBS 58) -- The Milwaukee County Sheriff's Office (MCSO) is investigating the death of a man who died in police custody Tuesday morning, Aug. 18. 

Officials say the 45-year-old man died shortly after being transported from the West Allis Police Department to the Milwaukee County Jail. 

The man was initially cleared by nursing staff during the booking process, according to the sheriff's office, however shortly before 8:30 a.m., he told jail staff he had vomited and wasn't feeling well.

Nurses determined he should be taken to a hospital for further evaluation, and as an ambulance and deputy escort prepared to take him, the sheriff's office says the man "experienced a medical emergency," going pulseless and not breathing. They say first responders attempted lifesaving measures, but the man was pronounced dead at 9:30 a.m.

Deputies initially picked up the man from the West Allis Police Department at 4:25 a.m. Tuesday on MCSO warrants, according to the sheriff's office, and the process of booking him began on charges of operating while revoked, operating while intoxicated 2nd, operating with a prohibited alcohol content, and ignition interlock device tampering. 

The Waukesha County Sheriff's Office is investigating the man's death.