Just after 19:00 BST Mr Tomlinson is seen on CCTV walking up King William Street and approaching a police cordon opposite the Bank of England. It is thought the 47-year-old wanted to get through and continue his walk home from work, however, police refused to let him do so.
A short time later, Mr Tomlinson is seen on CCTV walking into Royal Exchange Passage.
The IPCC statement confirms a number of witnesses have since described seeing him there, "getting caught up in a crowd and being pushed back by police officers".
"This is the aspect of the incident that the IPCC is now investigating," the statement reads.
Minutes later Mr Tomlinson is seen on CCTV walking back onto Cornhill from Royal Exchange Passage. He walks for about three more minutes, before collapsing on Cornhill.