At least 21 people have been killed, including 19 children in the school shooting in the small town of Uvalde in Texas.

All indications are that the perpetrator, a student from one of the city's high schools, acted alone.

He was killed by police in connection with the shooting. 

The 18-year-old Salvador Ramos was singled out as the perpetrator.

According to the city governor, he must have been armed with a pistol, and possibly also a rifle.

Just before he left for school, he shot his own grandmother.

However, the details of whether or not the grandmother survived differ. 

Before the school attack, Salvador Ramos must have indicated on social media that an attack could come, reports AP.

He is also said to have published photos of the weapons used in the shooting on Instagram.

Another user, a girl living in Los Angeles, is tagged in the photo, reports the NY Times.

She describes Ramos as a total stranger.

He is said to have sent several cryptic messages to her on Instagram and, among other things, written that he has "a little secret".

Just hours before he shot dead 21 people, he wrote "I'm about to."

No motive behind the act is known yet.

Ramos is said to have had problems with drugs and been weapon-fixed.

According to local media, he has previously made threats to his surroundings, reports SVT's US correspondent Stefan Åsberg. 

- It was a person who did not have very many friends, they say here.