President Donald Trump said Monday he believed the Texas church shooting was caused by a "mental health problem," and not because of a problem with domestic gun laws.

When asked whether U.S. gun control measures could have been the key to the Texas shooting, Trump replied, "Mental health is your problem here."

"This isn't a guns situation," he said, before adding, "This is a mental health problem at the highest level. It's a very, very sad event."

At least 26 people were killed and about 20 others were wounded after a gunman opened fire during a Sunday service at a Texas church. The victims ranged in age from 5 to 72-years-old.

Speaking at a joint press conference in Tokyo, Japan, alongside Prime Minister Shinzo Abe, Trump described the shooter as "a very deranged individual."