At least eight people have been confirmed dead after a gunman opened fire on Friday at a high school in the Texas state of Texas.
In a brief statement on Twitter, Trump said the situation in Texeas was not good.
The attack took place at the Santa Fe high school in Santa Fe, a town about 50 kilometers south of the city of Houston.
US media reported that among the dead are many students who study in the school shooting.
Chief of Harris, Ed Gonzalez, said one person was arrested for the incident.
Up to now there is no information available on the person executed.