It is definitely per capita. There is no question the US has one of the highest rates of gun violence per capita of developed countries. This table is out of date, but it show that in 1994 the US had the highest rate of gun deaths per capita of all thr countries surveyed.
The gun-related deaths per 100,000 people in 1994 by country were as follows:
U.S.A. 14.24
Brazil 12.95
Mexico 12.69
Estonia 12.26
Argentina 8.93
Northern Ireland 6.63
Finland 6.46
Switzerland 5.31
France 5.15
Canada 4.31
Norway 3.82
Austria 3.70
Portugal 3.20
Israel 2.91
Belgium 2.90
Australia 2.65
Slovenia 2.60
Italy 2.44
New Zealand 2.38
Denmark 2.09
Sweden 1.92
Kuwait 1.84
Greece 1.29
Germany 1.24
Hungary 1.11
Ireland 0.97
Spain 0.78
Netherlands 0.70
Scotland 0.54
England and Wales 0.41
Taiwan 0.37
Singapore 0.21
Mauritius 0.19
Hong Kong 0.14
South Korea 0.12
Japan 0.05
Gun Deaths - United States Tops The List
Even allowing for statistical quibbles, it's undeniably way up there.