Richard Biehl, the Chief of Police in Dayton, Ohio, said that Connor Betts, the 24-year-old responsible for the shooting overnight Saturday in the city’s entertainment district, wore a bulletproof vest, mask and hearing protection.

Betts carried at least 100 rounds as he opened fire, said Biehl, according to The Associated Press.

The shooter killed his sister and eight others in less than 30 seconds before police fatally shot him, he added.

Biehl said he could not yet answer why Betts carried out the shooting.

He added the .223-caliber rifle Betts used was ordered online from Texas and transferred to Betts at a firearms dealer in the area.

Officials say 27 more people were wounded in the shooting attack, which began a little past 1:00 a.m., either by gunfire or as they fled.

It was the second mass shooting in the US in less than 24 hours.

Hours before the shooting in Dayton, a mass shooting occurred in a Walmart in El Paso, Texas, killing 20 and injuring 27.

Responding on Sunday to the two shootings, President Donald Trump told reporters that "hate has no place in our country".

The president, who added that he will have a statement on Monday about the shootings, told reporters he had spoken to the FBI, Attorney General William Barr, and members of Congress about what can be done to prevent such violence.