A man in Texas has been charged following a potentially racially-motivated attack which left 20 people dead.
Nine people also died in another shooting in Ohio - where the gunman was killed by police.
Donald Trump's condemned the two mass shootings saying hate has no place in America.
The US president's been accused of stoking anti-immigrant sentiment, but he has another theory:
This is also a mental illness problem. If you look at both of these cases, this is mental illness. These are really people that are very, very, seriously mentally ill.
A crowd in Ohio has heckled the State Governor during his speech at a vigil following a mass shooting.
Shouts of "Make a change" and "Do something" were directed at Mike DeWine.