A homeless man turned in a lost backpack he found at South Bay Mall in Dorchester last night — a backpack Boston police said contained $2,400 cash and $39,500 in American Express Travelers Cheques.

The very good Samaritan told officers he lives at a Boston shelter.

The man, who police declined to identify by name, flagged down officers about 5:45 last night and told them he found the black backpack in front of TJ Maxx. Police said that in addition to the money, the backpack contained passports “and various personal papers.”

Police were contacted an hour later by a mall customer reporting he’d lost a backpack “containing a large sum of money.”

Police said the rightful owner was identified by his Republic of China passport and the property was returned to him.